Description:BACKGROUND
[0001] Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to being prior art by inclusion in this section.
Field of the invention:
[0002] The present invention relates to permanent magnet direct current (PMDC) motors, and more particularly to an integrated motor architecture combining a planar or radial commutator structure with a sensor-less rotor position detection system based on current ripple analysis.
Discussion on related field:
[0003] Permanent magnet direct current (PMDC) motors are widely used in industrial, automotive, and consumer applications due to their efficiency, compact size, and favourable torque characteristics. Their operation depends on effective commutation of armature current and accurate detection of rotor position. Existing solutions achieve these functions through either mechanical commutation or electronic control using position sensors or estimation techniques, each presenting inherent limitations affecting performance, reliability, and design flexibility.
[0004] In conventional PMDC motors, commutation is performed by means of a segmented cylindrical commutator and carbon brushes. As the rotor rotates, the brushes maintain sliding contact with successive segments, reversing current direction in the armature windings to sustain continuous torque. While simple and widely adopted, this approach relies on continuous mechanical contact.
[0005] Such contact leads to frictional wear, requiring periodic maintenance and replacement. Electrical arcing at the interface generates electromagnetic interference and accelerates surface degradation, resulting in reduced commutator uniformity, increased vibration, and acoustic noise.
[0006] Electronically commutated systems address these issues by using rotor position feedback from sensors such as Hall-effect devices, encoders, or resolvers. Although eliminating brush wear, these systems increase component count, wiring complexity, and assembly precision requirements. Additionally, sensors are susceptible to thermal drift, vibration, contamination, and electromagnetic interference, which can impair accuracy and reliability. They also add cost and introduce supply-chain dependencies.
[0007] Sensor-less methods infer rotor position from electrical signals such as back electromotive force or current ripple. While reducing hardware, these approaches often require complex processing, higher computational resources, or are ineffective at low speeds where signal quality is insufficient.
[0008] Accordingly, there remains a need for a PMDC motor architecture that eliminates mechanical wear, avoids sensor-related complexity, and supports compact design, while maintaining accurate commutation and reliable rotor position detection across the full operating range.
SUMMARY
[0009] The present invention provides a Permanent Magnet Direct Current (PMDC) motor equipped with a planar commutator mechanism that enables accurate rotor position estimation without reliance on dedicated external position sensors such as Hall-effect sensors or optical encoders.
[0010] The system includes a housing configured to receive at least a portion of the components. A shaft extends through the housing, defining an axis of rotation and having a proximal end and a distal end. An armature is coaxially mounted proximate to the proximal end of the shaft. A flat planar commutator is coaxially mounted on the shaft and comprises a plurality of conductive segments separated by intermediate insulative segments arranged in a planar configuration.
[0011] A Printed Circuit Board (PCB) is coaxially disposed proximate to the distal end of the shaft. A pair of brushes is configured to interact with at least a portion of the flat planar commutator to transfer electrical current to the armature windings. A pair of engagement members is disposed between the PCB and the brushes. These engagement members are configured to perform two functions that is maintaining a continuous physical contact between the brushes and the flat planar commutator during operation and enabling electrical communication between the brushes and the PCB.
[0012] During rotation of the flat planar commutator, each insulative segment passing across the brushes causes a momentary dip in the electric current, thereby producing a characteristic current ripple. The PCB is configured to detect and count the number of such current ripples and the number of rotation of the motor. Upon detection of a predetermined count of current ripples, the PCB controls the PMDC motor to execute a predetermined number of rotations, thereby enabling precise estimation of the rotor position and controlled angular displacement of the shaft.
[0013] The disclosed arrangement offers a compact, cost-effective, and sensor-less rotor position estimation solution suitable for applications demanding precise rotational control of a PMDC motor.
[0014] In an alternate embodiment, the present invention further provides a PMDC motor with a radial commutator mechanism. The system is structurally similar to the system, with the flat planar commutator replaced by a radial commutator mounted coaxially on the shaft, and the pair of brushes replaced by a pair of radial brushes oriented radially with respect to the axis of rotation. The radial commutator comprises a plurality of conductive segments separated by intermediate insulative segments, arranged alternately around the circumference of the outer cylindrical surface of the radial commutator.
[0015] In the system, the pair of engagement members are connected to an end cap 1306 configured to seal the PMDC motor, and the PCB may be positioned outside the motor arrangement. During rotation of the radial commutator, each insulative segment passing across the radial brushes causes a momentary dip in the electric current, thereby producing a characteristic current ripple. The PCB detects and counts the current ripples in the same manner as described for the system, enabling sensor-less rotor position estimation and precise rotational control of the system.
BRIEF DESCRIPTION OF DRAWINGS
[0016] This disclosure is illustrated by way of example and not limitation in the accompanying figures. Elements illustrated in the figures are not necessarily drawn to scale, in which like references indicate similar elements, and in which:
[0017] FIG. 1 illustrates a perspective view of a PMDC motor with a planar commutator mechanism 100, in accordance with an embodiment;
[0018] FIG. 2A illustrates an exploded view of the PMDC motor with a planar commutator mechanism 100, in accordance with an embodiment;
[0019] FIG. 2B illustrates a cross-sectional view of the PMDC motor with a planar commutator mechanism 100 with a housing 208, in accordance with an embodiment;
[0020] FIG. 3 illustrates a perspective view of an armature 102, in accordance with an embodiment;
[0021] FIG. 4 illustrates a perspective view of a flat planar commutator 104, in accordance with an embodiment;
[0022] FIG. 5 illustrates a perspective view of a pair of brushes 110, in accordance with an embodiment;
[0023] FIG. 6 illustrates a perspective view of a PCB 108, in accordance with an embodiment;
[0024] FIG. 7 illustrates a perspective view of an engagement housing 204 with a rectangular passage 702, in accordance with an embodiment;
[0025] FIG. 8 illustrates an assembled view of the PMDC motor with a planar commutator mechanism 100 without a housing 208, in accordance with an embodiment;
[0026] FIG. 9 illustrates an assembled view of the PCB 108 with the pair of brush 110, a pair of engagement members 202, in accordance with an embodiment; and
[0027] FIG. 10 illustrates a cross-sectional view of the PMDC motor with a planar commutator mechanism 100 without a housing 208, in accordance with an embodiment;
[0028] FIG. 11 illustrates a block diagram of the PCB 108, in accordance with an embodiment;
[0029] FIG. 12 illustrates a flowchart 1200, in accordance with an embodiment;
[0030] FIG. 13A illustrates a planar view of the PMDC motor with a radial commutator mechanism 1300, in accordance with an alternate embodiment;
[0031] FIG. 13B illustrates a cross-sectional view of the PMDC motor with the radial commutator mechanism 1300, in accordance with the alternate embodiment;
[0032] FIG. 14 illustrates a perspective view of a radial commutator mechanism 1300 without the housing 208, in accordance with the alternate embodiment; and
[0033] FIG. 15 illustrates a perspective view of the radial commutator 1302 along with the pair of radial brushes 1304, in accordance with the alternate embodiment.
DETAILED DESCRIPTION
[0034] The foregoing detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show illustrations in accordance with example embodiments. These example embodiments, which may herein also be referred to as “examples,” are described in enough detail to enable those skilled in the art to practice the present subject matter. However, it may be apparent to one with ordinary skill in the art, that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. The embodiments can be combined, other embodiments can be utilized, or structural, logical, and design changes can be made without departing from the scope of the claims. The foregoing detailed description is, therefore, not to be taken in a limiting sense, and the scope is defined by the appended claims and their equivalents.
[0035] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one. In this document, the term “or” is used to refer to a nonexclusive “or” such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated.
[0036] In the embodiments that shall be discussed, components may define a circular cross-section. However, the components may not be limited to a circular profile and may define any geometrical cross-section or combination of different geometrical cross-sections.
[0037] In an embodiment, referring to FIGs. 1-2, a PMDC motor with a planar commutator mechanism 100 (hereafter referred to as "system 100") is disclosed. The system 100 comprises a housing 208 (Not shown in the FIGs), a shaft 106, an armature 102, a flat planar commutator 104, a printed circuit board (PCB) 108, a pair of brushes 110, a pair of engagement members 202, a pair of engagement housings 204, a PCB holder 206, and a stator 210.
[0038] In an embodiment, Referring to FIG. 1, the housing 208 may be configured to receive at least a portion of the components. The housing 208 may be a structurally reinforced enclosure that serves as the primary structural member of the system 100 and provides mounting support for both rotational and stationary components.
[0039] In an embodiment, the system 100 further comprises a stator 210 received within the housing 208. The stator 210 may comprise at least one pair of permanent magnets disposed circumferentially around the armature 102. The permanent magnets of the stator 210 may be configured to generate a static magnetic field within the internal space of the housing 208, wherein the generated magnetic field interacts electromagnetically with the current-carrying armature windings 302 during rotation, thereby producing the rotational torque that drives the shaft 106.
[0040] In an embodiment, the permanent magnets of the stator 210 may be fixedly secured to the inner surface of the housing 208 in a diametrically opposed arrangement, ensuring a uniform and symmetric magnetic field distribution around the armature 102. The stator 210 may be fabricated from a high-magnetic-permeability material configured to enhance the flux density within the air gap between the stator 210 and the armature 102, thereby improving the electromagnetic efficiency of the system 100.
[0041] In an embodiment, referring to FIG. 1, the shaft 106 may define a proximal end and a distal end, along an axis 112 of rotation. The shaft 106 forms the central rotational axis 112 of the system 100 and may be configured to transmit the mechanical output torque of the motor to an external load.
[0042] In an embodiment, the shaft 106 may be fabricated from a high-strength metallic material and may be supported within the housing 208 by one or more bearing elements to ensure concentricity and smooth rotational movement. The proximal end of the shaft 106 may be configured to couple to the armature 102, and the distal end may be the output end extending beyond the housing 208 for mechanical coupling to the driven component.
[0043] In an embodiment, referring to FIG. 3, the armature 102 may be mounted coaxially proximate to the proximal end of the shaft 106. The armature 102 may be configured to convert electrical energy into electromagnetic energy, wherein the interaction between the armature 102 and the stator 210 produces rotational torque.
[0044] In an embodiment, the armature 102 may be provided with a plurality of windings 302 disposed around the armature core. The windings 302 may be made of copper wire, configured to assist in energy conversion by generating an electromagnetic field upon passage of electrical current. The armature 102 may be provided with a central rectangular through hole 304 configured to receive at least a portion of the shaft 106, thereby enabling coaxial mounting of the armature 102 on the shaft 106.
[0045] In an embodiment, referring to FIG. 1, the flat planar commutator 104 may be mounted coaxially on the shaft 106, intermediate to the proximal and distal ends. The flat planar commutator 104 may be but not limited to a circular disc shape, wherein the diameter of the flat planar commutator 104 is larger than the diameter of the armature 102. This circular disc-shaped, planar configuration distinguishes the flat planar commutator 104 from conventional cylindrical commutators and enables a more compact and low-profile motor architecture with reduced axial length. The flat planar commutator 104 may be positioned between the armature 102 and the PCB 108, wherein a first side of the flat planar commutator 104 faces the armature 102, and a second side of the flat planar commutator 104 is configured to interface with the pair of brushes 110.
[0046] In an embodiment, referring to FIG. 4, the flat planar commutator 104 may be provided with a plurality of conductive segments 402 separated by intermediate insulative segments 404.
[0047] In an embodiment, the conductive segments 402 may be fabricated from an electrically conductive material such as copper, and the insulative segments 404 may be fabricated from a non-conductive material. The arrangement of conductive segments 402 and insulative segments 404 of the flat planar commutator 104 defines the commutation pattern, wherein the movement of the insulative segments 404 across the pair of brushes 110 generates periodic dips in the electrical current, each of which corresponds to a current ripple.
[0048] In an embodiment, each conductive segment 402 of the flat planar commutator 104 may be defined as an annular sector of a circular commutator disc. The annular sector geometry ensures that each conductive segment 402 subtends an equal arc angle at the centre of the flat planar commutator 104, thereby promoting uniform current distribution across the commutator face as the pair of brushes 110 traverses each segment during rotation. The insulative segments 404, disposed intermediate to the conductive segments 402, may be configured to separate adjacent conductive segments 402 and define the commutation boundaries. The area of each conductive segment 402 may be larger than the area of each insulative segment 404, ensuring that the duration of electrical contact per commutation cycle is greater than the interruption duration, thereby minimising torque ripple and maintaining consistent motor output.
[0049] In an embodiment, the flat planar commutator 104 may be provided with a through hole 406 configured to receive at least a portion of the shaft 106, thereby enabling secure coaxial mounting of the flat planar commutator 104 on the shaft 106. The flat planar commutator 104 may rotate along with the shaft 106 and the armature 102 as a unified rotor assembly.
[0050] In an embodiment, the system 100 provides a compact and low-profile motor architecture by virtue of the flat planar commutator 104 being configured as a circular disc disposed perpendicular to the axis 112 of rotation, rather than as a segmented cylindrical structure extending axially along the shaft 106. This planar configuration substantially reduces the overall axial length of the system 100 relative to conventional PMDC motors of comparable power rating, thereby enabling integration of the system 100 within space-constrained applications where axial envelope is a limiting design parameter.
[0051] In an alternate embodiment (a system 1300), referring to FIG. 13B, the motor incorporates a radial commutator 1302. Both embodiments share a common PCB-based sensor-less current ripple detection and rotor position estimation architecture, as described herein.
[0052] In the alternate embodiment, referring to FIGs. 13A and 13B, a PMDC motor with a radial commutator mechanism 1300 (hereafter referred to as “system 1300”) is disclosed. The system 1300 is structurally similar to the system 100, with the flat planar commutator 104 replaced by a radial commutator 1302, and the pair of brushes 110 replaced by a pair of radial brushes 1304 oriented radially with respect to the axis 112 of rotation.
[0053] In the alternate embodiment, referring to FIG. 14, the radial commutator 1302 may be mounted coaxially on the shaft 106. The radial commutator 1302 may be configured as a cylindrical body and may be provided with a through hole configured to receive at least a portion of the shaft 106, thereby enabling secure coaxial mounting of the radial commutator 1302 on the shaft 106. The outer cylindrical surface of the radial commutator 1302 may be provided with a plurality of conductive segments 1402 separated by intermediate insulative segments 1404, arranged alternately around the circumference of the outer cylindrical surface and extending in a direction parallel to the axis 112 of rotation of the shaft 106. The radial commutator 1302 may rotate along with the shaft 106 and the armature 102 as a unified rotor assembly.
[0054] In the alternate embodiment, referring to FIG. 14, each conductive segment 1402 of the radial commutator 1302 may be defined as a rectangular or trapezoidal strip extending along the axial length of the outer cylindrical surface and subtending an equal arc angle at the centre of the radial commutator 1302. The insulative segments 1404, disposed intermediate to the conductive segments 1402, may be configured to separate adjacent conductive segments 1402 and define the commutation boundaries. The area of each conductive segment 1402 may be larger than the area of each insulative segment 1404, ensuring that the duration of electrical contact per commutation cycle is greater than the interruption duration, thereby minimising torque ripple and maintaining consistent motor output.
[0055] In the alternate embodiment, referring to FIG. 13A, the system 1300 provides a conventional cylindrical motor architecture, in contrast to the low-profile disc-shaped configuration of the system 100. This radial configuration conforms to the standard PMDC motor form factor, enabling the system 1300 to serve as a drop-in replacement for conventional PMDC motors where radial commutator geometry is mandated by legacy mechanical interface requirements or design conventions, while incorporating the sensor-less rotor position estimation architecture of the present invention.
[0056] In an embodiment, referring to FIG. 2, the PCB 108 may be disposed coaxially proximate to the distal end of the shaft 106. The PCB 108 may be provided with one or more processors 1114, configured to electrically determine a number of rotations of the flat planar commutator 104 by calculating a plurality of current ripples generated during motor operation. The PCB 108 is a stationary component that remains fixed relative to the rotating shaft 106, while the flat planar commutator 104 rotates above the pair of brushes 110 that are mounted on the PCB 108.
[0057] In an embodiment, referring to FIG. 6, the PCB 108 may be provided with a circular through hole 602, configured to receive at least a portion of the shaft 106 along the axis 112 of rotation.
[0058] In an embodiment, the PCB 108 may be detachably connected to at least a portion of a PCB holder 206, wherein the PCB holder 206 may be configured to receive at least a portion of the housing 208. The PCB holder 206 may be configured to fixedly position the PCB 108 within the system 100, ensuring accurate and consistent alignment of the pair of brushes 110 with respect to the flat planar commutator 104.
[0059] In an embodiment, referring to FIG. 5, the pair of brushes 110 may be received by the PCB 108 and configured to slidably interact with at least a portion of the flat planar commutator 104. Each brush 110 of the pair of brushes 110 may comprise a cylindrical base portion 504 and a rectangular contact portion 502. The cylindrical base portion 504 may be configured to be received within at least a portion of the engagement members 202, thereby enabling the engagement members 202 to exert an axial biasing force on the brush 110. The rectangular contact portion 502 may be configured to continuously traverse at least a portion of the flat planar commutator 104 on its second side, thereby enabling sliding electrical contact with the conductive segments 402 and transition across the insulative segments 404.
[0060] In an embodiment, the pair of brushes 110 may be oriented along the axis 112 of rotation, such that each brush 110 contacts the flat planar commutator 104 in a plane perpendicular to the axis 112 of rotation. This axial orientation of the pair of brushes 110 ensures that the rectangular contact portion 502 of each brush 110 interfaces with the second side of the flat planar commutator 104, wherein the contact force is directed along the axis 112. The perpendicular bearing orientation maximises the contact area between the pair of brushes 110 and the conductive segments 402 of the flat planar commutator 104, thereby reducing contact resistance, minimising electrical losses, and promoting uniform wear across the contact surface of each brush 110.
[0061] In an embodiment, the pair of brushes 110 may be configured to transfer electrical power from the stationary terminals of the PCB 108 to the rotating flat planar commutator 104 and onwards to the armature windings 302. This sliding contact between the pair of brushes 110 and the flat planar commutator 104 enables both the commutation function and the current ripple generation utilised for sensor-less position detection.
[0062] In an embodiment, the perpendicular orientation of the pair of brushes 110 relative to the second side of the flat planar commutator 104, in combination with the annular sector geometry of the conductive segments 402 and the axial biasing force exerted by the engagement members 202, ensures a substantially uniform contact area and contact pressure distribution across the brush-commutator interface throughout the operational life of the system 100. This arrangement reduces contact resistance, minimises electrical losses at the commutation interface, promotes uniform wear of the rectangular contact portion 502 of each brush 110, and correspondingly extends the service life of the pair of brushes 110 and the flat planar commutator 104.
[0063] In the alternate embodiment, referring to FIG. 15, the pair of radial brushes 1304 may be configured to slidably interact with at least a portion of the outer cylindrical surface of the radial commutator 1302. The pair of radial brushes 1304 may be oriented in a radially inward direction with respect to the shaft 106, such that each radial brush 1304 bears against the outer cylindrical surface of the radial commutator 1302 in a radial direction perpendicular to the axis 112 of rotation, in contrast to the axial orientation of the pair of brushes 110 in the system 100. This radial orientation maximises the contact area between the pair of radial brushes 1304 and the conductive segments 1402 of the radial commutator 1302, thereby reducing contact resistance and minimising electrical losses at the commutation interface.
[0064] In an embodiment, the pair of engagement members 202 may be operably connected to the PCB 108 and configured to maintain continuous contact between the pair of brushes 110 and at least a portion of the flat planar commutator 104. The pair of engagement members 202 may be but not limited to springs, configured to exert axial biasing force on the pair of brushes 110 along the axis 112 to maintain continuous contact between the pair of brushes 110 and the second side of the flat planar commutator 104. The axial biasing force applied by the engagement members 202 ensures that the contact between the brushes 110 and the flat planar commutator 104 is maintained consistently under varying operating conditions, including vibration and thermal expansion, thereby preventing intermittent contact or loss of electrical continuity.
[0065] In an embodiment, in addition to maintaining continuous contact between the pair of brushes 110 and the flat planar commutator 104, the pair of engagement members 202 may be further configured to enable electrical communication between the pair of brushes 110 and the PCB 108. The pair of engagement members 202, being disposed between the PCB 108 and the pair of brushes 110, may serve as electrically conductive pathways, wherein the current flowing through the pair of brushes 110 from the flat planar commutator 104 is conducted through the engagement members 202 to the PCB 108. This dual function of the engagement members 202, combining mechanical biasing with electrical conductivity, simplifies the internal wiring architecture of the system 100 and reduces the number of discrete electrical connection elements required within the assembly.
[0066] In an embodiment, the spring-based engagement members 202 may be fabricated from a resilient metallic material such as stainless steel or spring steel and may be selected to provide a predetermined spring force sufficient to ensure consistent brush-commutator contact across the full operating temperature range and speed range of the system 100. This configuration of the engagement members 202 enables uniform load distribution on the rectangular surface portion 502 of each brush 110, thereby minimising uneven wear and ensuring stable current transfer throughout the operational life of the system 100.
[0067] In an alternate embodiment, the pair of engagement members (202) may not be limited to springs and may include other resilient or biasing elements capable of exerting a continuous axial force on the pair of brushes (110). Such alternatives may include, but are not limited to, leaf springs configured to apply a lateral or axial bending force on the brushes (110), torsion springs configured to apply a rotational biasing force translated into axial brush displacement, elastomeric compression elements such as rubber or silicone pads providing compressive biasing force, or magnetic repulsion elements utilising permanent magnets to generate a non-contact axial biasing force on the brushes (110). The selection of the engagement member (202) type may be based on operational requirements such as available space, desired biasing force magnitude, thermal operating conditions, and assembly constraints of the system (100).
[0068] In the alternate embodiment, referring to FIG. 13B, the pair of engagement members 202 may be connected to an end cap 1306 of the system 1300, wherein the end cap 1306 may be configured to seal the PMDC motor. The pair of engagement members 202 may be springs, configured to exert a radially inward biasing force on the pair of radial brushes 1304 to maintain continuous contact between the pair of radial brushes 1304 and the outer cylindrical surface of the radial commutator 1302. The radially inward biasing force applied by the engagement members 202 ensures that the contact between the radial brushes 1304 and the radial commutator 1302 is maintained consistently under varying operating conditions, including vibration and thermal expansion, thereby preventing intermittent contact or loss of electrical continuity.
[0069] In an embodiment, referring to FIG. 2, the pair of engagement members 202 may be housed within a pair of engagement housings 204, wherein each engagement housing 204 may be received on the PCB 108. The engagement housing 204 may be but not limited to rectangular shape and may be provided with a rectangular passage 702 configured to detachably receive one of the pair of engagement members 202 and the corresponding brush 110. The rectangular passage 702 guides the translational movement of the brush 110 along the axis 112, ensuring that the brush 110 is constrained against undesired rotational or lateral displacement during motor operation.
[0070] In an embodiment, referring to FIGs. 8-9, the one or more processors 1114 of the PCB 108 may be configured to count the number of current ripples detected during rotation of the flat planar commutator 104 and also determine the number of rotations of the flat planar commutator 104. The one or more processors 1114 of the PCB 108 may further be configured to compare the counted ripples against a predetermined ripple count corresponding to the desired number of rotations of the system 100.
[0071] In an embodiment, referring to FIGs. 8-9, the one or more processors 1114 of the PCB 108 may be configured to terminate or modify operation of the system 100 upon reaching the predetermined ripple count. Each complete rotation of the flat planar commutator 104 generates a number of current ripples equal to the number of insulative segments 404 traversed by the pair of brushes 110. Consequently, the predetermined ripple count is calculated based on the number of conductive segments 402 of the flat planar commutator 104 and the desired number of motor rotations.
[0072] In an embodiment, the PCB 108 may comprise a current sensing element 1104 configured to monitor a supply current waveform of the PMDC motor and detect each current ripple as a voltage drop thereacross. The current sensing element 1104 may be electrically interposed in the supply current path of the armature 102, wherein the voltage drops generated across the current sensing element 1104 is proportional to the instantaneous supply current drawn by the armature windings 302. As each insulative segment 404 of the flat planar commutator 104 traverses the pair of brushes 110, the momentary interruption of the current path results in a periodic dip in the supply current waveform, which is manifested as a corresponding voltage drop across the current sensing element 1104 and detected as a current ripple.
[0073] In an embodiment, the current sensing element 1104 of the PCB 108 may further comprise a sensor 1106, a filter circuit 1108, a comparator 1110, and a counter circuit 1112. The sensor 1106 may be configured to receive the supply current waveform. The filter circuit 1108 may be configured to attenuate electrical noise from the supply current waveform, thereby conditioning the waveform prior to ripple detection and improving the signal-to-noise ratio. The comparator 1110 may be configured to generate a pulse signal each time the voltage drops across the current sensing element 1104 exceeds a predetermined threshold voltage, wherein each such pulse signal corresponds to one detected current ripple. The counter circuit 1112 may be configured to accumulate a ripple count by incrementing a count value upon each pulse signal received from the comparator 1110. The PCB 108 may be further configured to accumulate the ripple count corresponding to the detected current ripples and generate a control signal to interrupt or modify the power supply to the PMDC motor when the accumulated ripple count equals a predetermined threshold count 1116 corresponding to a target rotor displacement.
[0074] In an embodiment, the predetermined threshold voltage of the comparator 1110 may be calibrated based on a nominal supply current of the PMDC motor, such that only voltage drops exceeding a defined percentage of the nominal supply current waveform are registered as current ripples by the counter circuit 1112. This calibration ensures that false signals arising from electrical noise, supply voltage fluctuations, or mechanical vibrations do not trigger false ripple counts, thereby maintaining the accuracy of the sensor-less rotor position estimation over the operating life of the system 100.
[0075] In an embodiment, the PCB 108 may further comprise a power switching element 1102 electrically interposed between a power supply and the armature 102. The power switching element 1102 may be configured to receive the control signal generated by the current sensing element 1104 and to selectively interrupt or modify the supply current to the armature 102 upon the accumulated ripple count reaching the predetermined threshold count 1116. The power switching element 1102 may be, but is not limited to, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a bipolar junction transistor, or a relay, selected based on the current and voltage ratings of the system 100. Upon receiving the control signal, the power switching element 1102 may open the supply circuit or reduce the drive voltage to the armature 102, thereby terminating or modifying the operation of the PMDC motor in accordance with the target rotor displacement.
[0076] In an embodiment, the arrangement of the flat planar commutator 104 and the pair of brushes 110 in close proximity to the PCB 108 defines a substantially shorter signal conduction path between the brush-commutator interface and the PCB 108, thereby enabling reliable detection of even low-amplitude current ripple signals, in contrast to conventional cylindrical commutator arrangements wherein the extended conduction path contributes to greater signal attenuation and losses.
[0077] In an embodiment, referring to FIG. 6, the PCB 108 may be configured to receive electrical connections 606 through the upper surface of the PCB 108, wherein the electrical connections 606 are configured for supplying electrical power to the armature windings 302 through the pair of brushes 110 and the flat planar commutator 104. The routing of electrical connections 606 facilitates a compact and organised electrical layout within the system 100.
[0078] In the alternate embodiment, referring to FIG. 15, the PCB 108 of the system 1300 detects, counts, and processes current ripples generated at the brush commutator interface of the radial commutator 1302 and the pair of radial brushes 1304 in the same manner as described with respect to the system 100.
ASSEMBLY
[0079] Having discussed the components of the system 100 in detail, the assembly and working of the system 100 will be presented in the following sections. The system 100 is a PMDC motor with a planar commutator mechanism, wherein electrical energy is converted into mechanical rotational motion by the interaction of the armature 102 and the stator 210, and wherein sensor-less rotor position estimation is achieved through current ripple counting by the PCB 108.
[0080] In an embodiment, in an assembled state, the shaft 106 defines the central axis 112 of rotation of the system 100, wherein the armature 102 is mounted coaxially at the proximal end of the shaft 106 and the flat planar commutator 104 is mounted coaxially intermediate the proximal and distal ends of the shaft 106. The armature 102, the flat planar commutator 104, and the shaft 106 together form the rotor assembly, which rotates within the housing 208 in response to the electromagnetic torque generated by the interaction between the energised armature windings 302 and the stator 210.
[0081] In an embodiment, the flat planar commutator 104 may be positioned such that its first side faces towards the armature 102 and its second side faces towards the PCB 108. The pair of brushes 110, received within the engagement housings 204 mounted on the PCB 108, may be in continuous slidable contact with the second side of the flat planar commutator 104. The pair of engagement members 202, housed within the rectangular passages 702 of the engagement housings 204, may be configured to apply a continuous axial biasing force along the axis 112 onto the pair of brushes 110, thereby ensuring uninterrupted sliding contact between the pair of brushes 110 and the flat planar commutator 104.
[0082] In an embodiment, the PCB 108 may be secured to the PCB holder 206, and the PCB holder 206 may be received within the housing 208 such that the PCB 108 is fixedly positioned in coaxial alignment with the shaft 106. This arrangement ensures consistent positional alignment between the pair of brushes 110 and the flat planar commutator 104 throughout the operational life of the system 100.
[0083] In an embodiment, the stator 210 may be disposed on the inner surface of the housing 208, radially surrounding the armature 102. The stator 210 provides the permanent magnetic field required for motor operation, and its interaction with the current-carrying armature windings 302 generates the rotational torque that drives the shaft 106.
[0084] In the alternate embodiment, the PCB 108 may be positioned outside the motor arrangement, in contrast to the system 100 wherein the PCB 108 is disposed coaxially proximate to the distal end of the shaft 106 within the housing 208.
[0085] In the alternate embodiment, in an assembled state of the system 1300, the armature 102, the radial commutator 1302, and the shaft 106 together form the rotor assembly, which rotates within the housing in the same manner as described with respect to the system 100.
[0086] In the alternate embodiment, the pair of engagement members 202 may be mounted in a radially opposed arrangement around the radial commutator 1302, such that each engagement member 202 guides a respective radial brush 1304 in a radially inward direction towards the outer cylindrical surface of the radial commutator 1302.
WORKING
[0087] Having discussed the assembly of the system 100 in detail, the working of the system 100 will be presented in the following section, with reference to FIGs 10-12.
[0088] In one embodiment, when electrical power is supplied to the system 100, the current flows from the electrical connections 606 through the pair of brushes 110, via the rectangular passages 702 of the engagement housings 204, into the conductive segments 402 of the flat planar commutator 104, and onwards to the armature windings 302. The interaction between the energised armature windings 302 and the permanent magnetic field established by the stator 210 generates an electromagnetic torque that drives the rotor assembly, comprising the armature 102, the flat planar commutator 104, and the shaft 106, in rotation about the axis 112. This step of energising the armature 102 by transferring current from the pair of brushes 110 to the armature 102, thereby causing rotation of the flat planar commutator 104, corresponds to step 1202 of FIG. 12.
[0089] In an embodiment, as the flat planar commutator 104 rotates, the pair of brushes 110 maintained in continuous contact with the second side of the flat planar commutator 104 by the axial biasing force of the engagement members 202, alternately traverse the conductive segments 402 and the insulative segments 404 in sequence. When the pair of brushes 110 is in contact with a conductive segment 402, current flows freely through the brush-commutator interface. When the pair of brushes 110 transitions across an insulative segment 404, the current path through that brush is momentarily interrupted, resulting in a periodic dip in the electrical current drawn by the motor. Each such dip in current corresponds to one current ripple. This step of generating a current ripple in response to the pair of brushes 110 traversing across the insulative segments 404 of the flat planar commutator 104 corresponds to step 1204 of FIG. 12.
[0090] In an embodiment, the supply current waveform of the PMDC motor is continuously monitored by the current sensing element 1104 of the PCB 108, wherein the current sensing element 1104 is electrically interposed in the supply current path of the armature 102. Each periodic dip in the supply current, caused by an insulative segment 404 traversing the pair of brushes 110 during rotation of the flat planar commutator 104, manifests as a corresponding voltage drop across the current sensing element 1104. The sensor 1106 of the current sensing element 1104 receives the supply current waveform and forwards the same to the filter circuit 1108, wherein the filter circuit 1108 attenuates electrical noise from the supply current waveform, thereby conditioning the waveform prior to ripple detection and improving the signal-to-noise ratio of the signal supplied to subsequent stages.
[0091] In an embodiment, the conditioned waveform from the filter circuit 1108 is supplied to the comparator 1110, wherein the comparator 1110 compares the voltage drop across the current sensing element 1104 against a predetermined threshold voltage. Each time the voltage drop exceeds the predetermined threshold voltage, the comparator 1110 generates a pulse signal corresponding to one detected current ripple. The predetermined threshold voltage of the comparator 1110 is calibrated based on a nominal supply current of the PMDC motor, such that only voltage drops exceeding a defined percentage of the nominal supply current waveform are registered as current ripples, thereby ensuring that false signals arising from electrical noise, supply voltage fluctuations, or mechanical vibrations do not trigger spurious pulses. This step of comparing the generated current ripple with the predetermined threshold voltage to produce a pulse corresponding to the current ripple corresponds to step 1206 of FIG. 12.
[0092] In an embodiment, the pulse signals generated by the comparator 1110 are received by the counter circuit 1112, wherein the counter circuit 1112 increments a count value upon each pulse signal received from the comparator 1110, thereby accumulating a ripple count. Since the number of current ripples generated per complete revolution of the flat planar commutator 104 is equal to the number of insulative segments 404 traversed by the pair of brushes 110 per revolution, the counter circuit 1112 determines the number of rotations of the flat planar commutator 104 based on the accumulated pulses. This step of determining the number of rotations of the flat planar commutator 104 using the counter circuit 1112, based on the produced pulse corresponding to the current ripple, corresponds to step 1208 of FIG. 12.
[0093] In an embodiment, the one or more processors 1114 of the PCB 108 are configured to calculate a total ripple count based on the produced pulses received from the comparator 1110 and the determined number of rotations of the flat planar commutator 104 obtained from the counter circuit 1112. The total ripple count thus represents the cumulative angular displacement of the rotor assembly from a reference position. This step of calculating the total ripple count based on the produced pulse and the determined number of rotations of the flat planar commutator 104 corresponds to step 1210 of FIG. 12.
[0094] In an embodiment, the one or more processors 1114 of the PCB 108 are further configured to evaluate the total ripple count against a predetermined threshold count 1116 corresponding to a target rotor displacement, and to generate one or more control signals upon the total ripple count reaching the predetermined threshold count 1116. The predetermined threshold count 1116 is determined based on the number of insulative segments 404 of the flat planar commutator 104 and a desired number of rotations of the PMDC motor, wherein each complete rotation of the flat planar commutator 104 generates a number of current ripples equal to the number of insulative segments 404 traversed by the pair of brushes 110 per revolution. This step of evaluating the total ripple count against the predetermined threshold value to generate one or more control signals corresponds to step 1212 of FIG. 12.
[0095] In an embodiment, the one or more control signals generated by the one or more processors 1114 are received by the power switching element 1102, wherein the power switching element 1102 is electrically interposed between a power supply and the armature 102. Upon receiving the one or more control signals, the power switching element 1102 selectively interrupts or modifies the supply current to the armature 102, thereby operating the PMDC motor according to a predefined criterion such as the target rotor displacement. The power switching element 1102 may, by way of non-limiting example, open the supply circuit or reduce the drive voltage to the armature 102, thereby terminating or modifying the operation of the system 100 accordingly. This step of modifying the current supply based on the generated one or more control signals to operate the motor according to the predefined criterion corresponds to step 1214 of FIG. 12.
[0096] In an embodiment, the foregoing operation enables precise angular positioning and controlled motor operation of the system 100 without the need for external position sensors such as Hall-effect sensors or optical encoders, since rotor position estimation is derived entirely from the current ripple signal generated at the brush-commutator interface and processed by the on-board signal chain of the PCB 108. The arrangement of the flat planar commutator 104 and the pair of brushes 110 in close proximity to the PCB 108 further defines a substantially shorter signal conduction path between the brush-commutator interface and the current sensing element 1104, thereby enabling reliable detection of even low-amplitude current ripple signals.
[0097] In an embodiment, the pair of engagement members 202 continuously exerts axial biasing force on the pair of brushes 110, maintaining uninterrupted contact between the pair of brushes 110 and the flat planar commutator 104 under varying mechanical and thermal operating conditions. This ensures that current ripple signals generated at the brush-commutator interface are clean, consistent, and reliably detectable by the PCB 108, thereby enabling accurate sensor-less position estimation throughout the operational life of the system 100.
[0098] In the alternate embodiment, referring to FIG. 13B, when electrical power is supplied to the system 1300, the current flows from the electrical connections through the pair of radial brushes 1304, via the engagement members 202, into the conductive segments 1402 of the radial commutator 1302, and onwards to the armature windings 302, thereby driving the rotor assembly in rotation about the axis 112.
[0099] In the alternate embodiment, referring to FIG. 15, as the radial commutator 1302 rotates, the pair of radial brushes 1304 alternately traverses the conductive segments 1402 and the insulative segments 1404 in a radial direction, generating current ripples in the same manner as described with respect to the system 100, which are detected and processed by the PCB 108 to enable sensor-less rotor position estimation of the system 1300.
[0100] In an embodiment, it is contemplated that the foregoing operation of the system 100 may equivalently be embodied as a method 1200 of controlling a motor, comprising the steps illustrated in FIG. 12, including energising the armature 102, generating the current ripple, comparing the generated current ripple with the predetermined threshold voltage to produce the pulse, determining the number of rotations of the flat planar commutator 104 using the counter circuit 1112, calculating the total ripple count, evaluating the total ripple count against the predetermined threshold value to generate the one or more control signals, and modifying the current supply based on the generated one or more control signals to operate the motor according to the predefined criterion.
[0101] Having described the detailed working of the system 100, it is evident that the controlled interaction between the flat planar commutator 104, the pair of brushes 110, the engagement members 202, the PCB 108, and the armature 102 ensures smooth commutation and consistent current ripple generation. The precise alignment of these components allows for efficient energy conversion, reliable sensor-less rotor position estimation, reduced electromagnetic interference, and extended operational life of the system 100.
[0102] The processes described above are described as a sequence of steps. This was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be rearranged, or some steps may be performed simultaneously.
[0103] Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the system and method described herein. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
[0104] Many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. It is to be understood that the description above contains many specifications, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the personally preferred embodiments of this invention. , Claims:We claim:
1. A PMDC motor with a planar commutator mechanism (100) comprising:
a housing (208) configured to receive at least a portion of the PMDC motor;
a shaft (106) defining an axis (112) of rotation, and a proximal end and a distal end along the axis (112) of rotation;
an armature (102) mounted coaxially proximate to the proximal end of the shaft (106);
a flat planar commutator (104) mounted coaxially on the shaft (106), wherein the flat planar commutator (104) comprises a plurality of conductive segments (402) separated by intermediate insulative segments (404);
a printed circuit board PCB (108) with one or more processors (1114) disposed coaxially proximate to the distal end of the shaft (106);
a pair of brushes (110) configured to interact with at least a portion of the flat planar commutator (104);
a pair of engagement members (202) disposed between the PCB (108) and the pair of brushes (110), configured to:
maintain a continuous contact between the pair of brushes (110) and at least a portion of the flat planar commutator (104); and
enable electrical communication between the pair of brushes (110) and the PCB (108);
wherein:
the one or more processors (1114) of the PCB (108) is configured to detect and count a number of current ripples caused by periodic dips in electric current, wherein each dip occurs as an insulative segment (404) of the flat planar commutator (104) traverses the pair of brushes (110) during rotation of the flat planar commutator (104); and
the one or more processors (1114) of the PCB (108) is configured to control the PMDC motor to execute a predetermined number of rotations upon detection of a predetermined count of the current ripples, thereby enabling estimation of rotor position.

2. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein each conductive segment (402) is defined as an annular sector of the flat planar commutator (104) which defines a circular profile.

3. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein the armature (102) is provided with windings (302), configured to assist in energy conversion, wherein the windings are made of copper wire.

4. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein the pair of engagement members (202) are springs, configured to exert axial biasing force on the pair of brushes (110) along the axis (112) to maintain continuous contact with at least a portion of the flat planar commutator (104).

5. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein each brush among the pair of brushes comprises:
a cylindrical base portion (504), configured to be received within at least a portion of the engagement members (202); and
a rectangular contact portion (502), configured to continuously interface at least a portion of the flat planar commutator (104).

6. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein the pair of engagement members (202) are housed within a pair of engagement housings (204) received on the PCB (108).

7. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 6, wherein each engagement housing (204) is rectangular in shape and defines a rectangular passage (702) configured to detachably receive a respective engagement member (202), and wherein the PCB (108) is configured to receive electrical connections (606) for supplying electrical power to the armature windings (302) through the pair of brushes (110) and the flat planar commutator (104).

8. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein the pair of brushes (110) are oriented along the axis (112) of rotation such that each brush (110) bears against the flat planar commutator (104) in a plane perpendicular to the axis (112) of rotation.

9. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, further comprising a stator (210) received within the housing (208), the stator (210) comprising at least one pair of permanent magnets disposed circumferentially around the armature (102) and configured to generate a magnetic field for electromagnetic interaction with the armature (102) during rotation.

10. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 1, wherein the PCB (108) comprises a current sensing element (1104) configured to:
monitor a supply current waveform of the PMDC motor; and
detect each current ripple as a voltage drop thereacross; and
the one or more processors (1114) of the PCB (108) is configured to:
accumulate a ripple count corresponding to the detected current ripples; and
generate a control signal to interrupt or modify power supply to the PMDC motor when the accumulated ripple count equals a predetermined threshold count (1116) corresponding to a target rotor displacement.

11. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 10, wherein the predetermined threshold count (1116) is determined based on the number of insulative segments (404) of the flat planar commutator (104) and a desired number of rotations of the PMDC motor.

12. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 10, wherein the current sensing element (1104) comprises:
a filter circuit (1108) configured to attenuate electrical noise from the supply current waveform;
a comparator (1110) configured to generate a pulse signal each time the voltage drop across the current sensing element (1104) exceeds a predetermined threshold voltage, wherein each pulse signal corresponds to one current ripple; and
a counter circuit (1112) configured to accumulate a ripple count by incrementing a count value upon each pulse signal received from the comparator (1110).

13. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 12, wherein the predetermined threshold voltage of the comparator (1110) is calibrated based on a nominal supply current of the PMDC motor, such that only voltage drops exceeding a defined percentage of the nominal supply current waveform are registered as current ripples.

14. The PMDC motor with the planar commutator mechanism (100) as claimed in claim 10, wherein the PCB (108) further comprises a power switching element (1102) electrically interposed between a power supply and the armature (102), the power switching element (1102) being configured to receive the control signal from the current sensing element (1104) and selectively interrupt or modify the supply current to the armature (102) upon the accumulated ripple count reaching the predetermined threshold count (1116).

15. A method (1200) of controlling a motor, the method comprising:
energizing an armature (102) by transferring current from a pair of brushes (110) to the armature (102), thereby causing rotation of a flat planar commutator (104);
generating a current ripple in response to the pair of brushes (110) traversing across insulative segments (404) of the flat planar commutator (104);
comparing the generated current ripple with a predetermined threshold voltage to produce a pulse corresponding to the current ripple;
determining a number of rotations of the flat planar commutator (104) using a counter circuit (1112), wherein the number of rotations is determined based on the produced pulse corresponding to the current ripple;
calculating a total ripple count based on the produced pulse and the determined number of rotations of the flat planar commutator (104);
evaluating the total ripple count against a predetermined threshold value to generate one or more control signals; and
modifying the current supply based on the generated one or more control signals to operate the motor according to a predefined criterion.

16. A PMDC motor with a radial commutator mechanism (1300) comprising:
a housing configured to receive at least a portion of the PMDC motor;
a shaft (106) defining an axis (112) of rotation, and a proximal end and a distal end along the axis (112) of rotation;
an armature (102) mounted coaxially proximate to the proximal end of the shaft (106);
a radial commutator (1302) mounted coaxially on the shaft (106), wherein the radial commutator (1302) comprises a plurality of conductive segments (1402) separated by intermediate insulative segments (1404), wherein the conductive segments (1402) and the insulative segments (1404) are arranged circumferentially on an outer cylindrical surface of the radial commutator (1302) and extend in a direction parallel to the axis (112) of rotation;
a printed circuit board PCB (108) with one or more processors (1114) disposed below an end cap (1306);
a pair of radial brushes (1304) configured to interact with at least a portion of the outer cylindrical surface of the radial commutator (1302) in a radial direction perpendicular to the axis (112) of rotation;
a pair of engagement members (202) disposed between the end cap (1306) and the pair of radial brushes (1304), configured to:
maintain a continuous contact between the pair of radial brushes (1304) and at least a portion of the outer cylindrical surface of the radial commutator (1302); and
enable electrical communication between the pair of radial brushes (1304) and the PCB (108) through the end cap (1306);
wherein:
the one or more processors (1114) of the PCB (108) is configured to detect and count a number of current ripples caused by periodic dips in electric current, wherein each dip occurs as an insulative segment (1404) of the radial commutator (1302) traverses the pair of radial brushes (1304) during rotation of the radial commutator (1302); and
the one or more processors (1114) of the PCB (108) is configured to control the PMDC motor to execute a predetermined number of rotations upon detection of a predetermined count of the current ripples, thereby enabling estimation of rotor position.

17. The PMDC motor with the radial commutator mechanism (1300) as claimed in claim 16, wherein each conductive segment (1402) is defined as a rectangular or trapezoidal strip extending along an axial length of the outer cylindrical surface of the radial commutator (1302) and subtending an equal arc angle at a centre of the radial commutator (1302).