Description:AN OFFSET ANGLE CALIBRATION SYSTEM FOR A MOTOR AND A METHOD THEREOF
FIELD OF THE INVENTION
[0001]
The present subject matter is related, in general to an offset angle 5 calibration system for a motor and a method thereof.
BACKGROUND OF THE INVENTION
[0002]
Typically, an electric motor, sometimes referred as a motor is a device that converts electrical energy into mechanical energy through the interaction of magnetic fields. The motor typically consists of two main components: a stationary 10 part called as a stator and a rotating part called as a rotor. The stator contains coils of wire that, when energized with an electrical current, generate a magnetic field. The rotor, often equipped with magnets or coils, experiences a force in the presence of the magnetic field, causing the rotor to rotate. This rotational motion is then harnessed for various applications, such as driving vehicles or powering devices. 15 By controlling the current supplied to the stator coils, the speed and direction of the motor can be precisely regulated. The fundamental principle underlying motor operation is electromagnetic induction, where the interaction between magnetic fields induces mechanical motion, illustrating the seamless conversion of electrical energy into mechanical work in the efficient functioning of electric motors. 20
[0003]
As a principal of physics, the electromagnetic torque produced by the motor is directly proportional to a flux generated by the stator, the flux generated by the torque, and sin ? where ? is angular difference between the flux generated by the stator and the rotor. Mathematically, it can be expressed as T=k·??s·?r·sin(?).
Here: 25
T is the torque generated by the motor;
k is a proportionality constant;
?s is the flux linkage of the stator;
3
?r is the flux linkage of the rotor; and
? is the angle between the stator and rotor flux linkages.
The sine function accounts for the fact that the torque is maximized when the two fluxes are perpendicular i.e., ?=90 degrees, and it is zero when they are parallel ?=0 degrees or 180 degrees. Therefore, to generate maximum torque from the motor it 5 is important to supply current to the stator windings perpendicular to the rotor position. Hence, it is important to calibrate accurate position of the rotor.
[0004]
Typically, during motor assembly in assembly line an encoder is mounted on a shaft of the motor. The encoder is a device comprising a small magnet which provides information relating to the rotational angle of the rotor. For the encoder to 10 provide accurate information relating the rotation position of the rotor, a north pole and the south pole of the encoder magnet and the rotor magnet should be aligned. However, during assembly of the motor it is challenging to mount the encoder at a specific alignment because it is time consuming and complex and requires specialized complex tools. 15
[0005]
In case, there is an angular difference between the poles of the encoder, and the rotor, the position of the rotor provided by the encoder will be at an offset angle which differs from the actual position of the rotor. It is important to estimate the position of the rotor correctly or accurately, so that the user can supply current or voltage input approximately perpendicular to the rotor position for maximum 20 torque output. For instance, in a scenario where the rotor's actual position differs by 90 degrees from the position indicated by the encoder, and the current input is supplied at 90 difference, the torque generated would be zero because sin 180 is equal to 0. In other words, the current supplied will be at 90 degrees difference with the rotor position indicated by the encoder, which results in 180 degrees angular 25 difference between the stator and rotor flux linkages. As the torque generation is contingent on the sine of 180 degrees therefore this results in no effective torque output.
4
[0006]
In view of the above, usually the offset angle of the rotor is calculated using a dynamo or an auxiliary motor, sometimes referred as secondary motor which is coupled with a primary motor for which the offset angle is to be calculated. Therefore, this means that the primary motor is operated in a no-load condition. The auxiliary motor is connected to a control unit. While the auxiliary motor starts 5 operating, the primary motor generates a back EMF in a sinusoidal wave form. The offset angle is calculated by the control unit at a peak position of the sinusoidal wave. Importantly, the conventional method of offset angle determination necessitates an auxiliary motor, and for measuring the offset angle of each primary motor, the primary motors are individually mechanically linked to the auxiliary 10 motor through nuts and bolts. This setup is complex in both operation, and maintenance. Further, this requires specialized training of assembly line personnels for accurate determination of the offset angle in a motor which makes the entire process time consuming. Moreover, if the secondary motor malfunctions, the entire system for offset angle calculation, including the control unit, must be replaced. 15
[0007]
Thus, in view of the above there is a need to determine the offset angle of the motor in simple, time efficient, accurately without need of any additional components such as an auxiliary dynamometer.
[0008]
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of 20 described systems with some aspects of the present disclosure, as set forth in the remainder of the present application and with reference to the drawings.
SUMMARY
[0009]
As per an embodiment of the present invention, a method of determining an offset angle of a motor unit, comprises the steps of: deaccelerating, the 25 motor unit after operating the motor unit at a predefined revolution per minute (RPM). Then, recording, a back EMF voltage of the motor unit while the motor unit is deaccelerating; and executing, an offset angle calibration method. The offset angle calibration method comprises the steps of: recording, a set of data relating the denoised back EMF voltage value corresponding to a time window 30
5
ranging from 1 to i. Then comparing, at least one of the set of data
corresponding to a predefined time window j with remaining set of data in time window i-j, if the value of the at least one of the set of data corresponding to the predefined time window is highest than the remaining set of data in time window i-j, estimating the corresponding angular position of an encoder; else, 5 if the voltage value of back emf at a time window k is highest. If the time window k is less than or equal to i, and more than 1 the predefined time window j is reset to a time window k and the offset angle calibration method is reiterated.
[00010]
As per an embodiment of the present invention, the recorded back EMF 10 voltage values of the motor unit is denoised before executing the offset angle calibration method.
[00011]
As per an embodiment of the present invention, wherein if the time window k is equal to 1, the offset angle calibration method is iterated in a subsequent positive cycle of back emf back EMF voltage value of the motor unit. 15
[00012]
As per an embodiment of the present invention, estimating the corresponding angular position of an encoder is converted into an electrical angle to estimate the offset angle of a motor unit.
[00013]
As per an embodiment of the present invention, a set of data corresponding to angular position of an encoder is recorded by the offset angle calibration 20 method till the RPM of the motor unit is zero and wherein the offset angle is determined by calculating an average value of set of data corresponding to the angular position of the encoder.
BRIEF DESCRIPTION OF THE DRAWINGS
[00014]
The present invention will become more fully understood from the detailed 25 description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
6
[00015]
Figure 1 illustrates a graphical representation of the relation between a flux generated by a stator, a rotor of a motor and an offset angle estimated by the encoder.
[00016]
Figure 2 illustrates a graphical representation of the recorded back emf and corresponding encoder angle as per an embodiment of the present invention. 5
[00017]
Figure 3 and Figure 4 illustrate a graphical representation of the recorded back emf of the motor unit as per an embodiment of the present invention.
[00018]
Figure 5 illustrates a graphical representation denoised back emf of the motor unit as per an embodiment of the present invention.
[00019]
Figure 6 illustrates a graphical representation of the denoised back emf of 10 the motor unit as per an embodiment of the present invention.
[00020]
Figure 7(a) and Figure 7(b) illustrate a graphical representation of the offset angle calibration method for the recorded back emf of the motor unit as per an embodiment of the present invention.
[00021]
Figure 8 illustrates a flow chart for determining an offset angle of a motor 15 unit as per an embodiment of the present invention.
[00022]
Figure 9(a) and Figure 9(b) illustrate a flow chart for executing an offset angle calibration method as per an embodiment of the present invention.
DETAILED DESCRIPTION
[00023]
The present disclosure may be best understood with reference to the 20 detailed figures and description set forth herein. Various embodiments are discussed below with reference to the figures. However, those skilled in the art will readily appreciate that the detailed descriptions given herein with respect to the figures are simply for explanatory purposes as the methods and systems may extend beyond the described embodiments. For example, the teachings presented, and the 25 needs of a particular application may yield multiple alternative and suitable approaches to implement the functionality of any detail described herein. Therefore,
7
any approach may extend beyond the particular implementation choices in the
following embodiments described and shown.
[00024]
References to “one embodiment,” “at least one embodiment,” “an embodiment,” “one example,” “an example,” “for example,” and so on indicate that the embodiment(s) or example(s) may include a particular feature, structure, 5 characteristic, property, element, or limitation but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element, or limitation. Further, repeated use of the phrase “in an embodiment” does not necessarily refer to the same embodiment.
[00025]
The present invention now will be described more fully hereinafter with 10 different embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather those embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the invention to those skilled in the art. 15
[00026]
The objective of the present invention is to enable determining the offset angle of a motor during assembly without the need for an auxiliary dynamo or secondary motor, thereby simplifying the overall process of estimating the offset angle. It is also an objective of the present invention to provide an economic solution to determine an offset angle of a motor unit by eliminating the need for 20 additional components such as an auxiliary dynamometer and reducing overall assembly time and offset angle determination complexity.
[00027]
It is further an objective of the present invention to eliminate the complexity of mechanically linking individual motor unit to an auxiliary motor through nuts and bolts, thereby providing a more streamlined and efficient approach 25 to offset angle determination of a motor unit. Further, the present invention aims to eliminate the requirement of exclusively trained personnels to determine the offset angle of the motor unit.
8
[00028]
In simple words, the present invention aims to address the limitations of existing methods of determining offset angle of a motor by providing a solution that is simple, time-efficient, economic, and accurately determines the offset angle of the motor without the need for an auxiliary dynamometer or complex mechanical linkages. 5
[00029]
The aforesaid and other advantages of the present subject matter would be described in greater detail in conjunction with the figures & embodiment in the following description.
[00030]
Figure 1 illustrates a graphical representation of the relation between a flux generated by a stator, a rotor of a motor and an offset angle estimated by the 10 encoder. Typically, the encoder (206, shown in fig 2) is mounted to a shaft of the motor unit (not shown). The primary function of the encoder (206) is to provide feedback on the rotor's position and speed to the control unit (shown in fig. 2). This feedback is crucial for the precise control and operation of the motor. As a principal of physics, the electromagnetic torque produced by the motor is directly 15 proportional to a flux linkages of the stator (not shown) and rotor (not shown). These flux linkages are influenced by the magnetic fields generated by the stator and rotor components of the motor. The torque is also dependent on an angle between the flux linkages of the stator and rotor. The sine of the angle (sin ?) is a crucial factor in the torque equation, indicating that torque is maximized when the 20 two fluxes are perpendicular (? = 90 degrees) and minimized when they are parallel (? = 0 degrees or 180 degrees). Mathematically, the electromagnetic torque (T) can be expressed as: Mathematically, it can be expressed as T=k·??s·?r·sin(?).
Here:
T is the torque generated by the motor; 25
k is a proportionality constant;
?s is the flux linkage of the stator;
?r is the flux linkage of the rotor; and
? is the angle between the stator and rotor flux linkages.
9
Therefore, to generate maximum torque from the motor it is important to supply current to the stator windings perpendicular to the rotor position. Hence, it is important to calibrate accurate position of the rotor.
In Figure 1(a), the alignment of the encoder (206) which determines direction of flux of the rotor ( ?_rotor_offset) corresponds precisely with the actual direction of 5 flux of the rotor (?_rotor_actual). This alignment indicates that the encoder (206) accurately estimates the rotor's position without any angular deviation. Consequently, in this scenario, the current supplied to the stator can be precisely delivered at a 90-degree angle concerning the rotor position. This particular angular alignment is crucial because, as per the motor torque equation, the torque output is 10 maximized when the stator and rotor flux linkages are perpendicular (? = 90 degrees). Therefore, by aligning the current input at 90 degrees to the rotor position indicated by the encoder (206), the motor can generate maximum torque efficiently. Further, as seen from fig. 1(b), the direction of the flux generated by the rotor as indicated by the encoder (206) is disposed at an angular difference of ? offset from 15 the actual direction of flux by the rotor. Thus, in this condition the current supplied to the stator is at an angular difference of ? offset + ? actual difference. This means than the torque output of the motor is not optimum or maximized, but the torque output can be precisely delivered at a 90-degree angle concerning the rotor position.
In Figure 1(b), the orientation of the flux generated by the rotor, as indicated by the 20 encoder (206) (?_rotor_offset), deviates at an angular difference of ?_offset from the actual direction of flux exhibited by the rotor (?_rotor_actual). Consequently, the current supplied to the stator is not aligned perfectly at 90 degrees with respect to the rotor position. Instead, it is supplied at an angular difference of ?_offset + ?_actual. This angular misalignment is critical because the torque output of the 25 motor, as governed by the torque equation, is optimized when the stator and rotor flux linkages are perpendicular (? = 90 degrees). When there is an offset angle (?_offset) introduced by the encoder (206), and it combines with the actual angular difference (?_actual) between the flux directions, the net result is an angular difference between the stator and rotor flux linkages that is not ideal for torque 30
10
maximization. In simpler terms, if the encoder (206) wrongly determines the rotor position and introduces an offset angle, and there is an existing actual angular difference between the rotor and stator flux, the cumulative effect is a less-than-optimal alignment for torque generation. In such a condition, the torque output of the motor is suboptimal, and it may not reach its maximum potential. 5
In Figure 1(c), the orientation of the flux generated by the rotor, as indicated by the encoder (206) (?_rotor_offset), deviates at an angular difference of ?_offset which is precisely 90 degrees from the actual direction of flux exhibited by the rotor (?_rotor_actual). Consequently, the current supplied to the stator is aligned 0 degrees with respect to the actual rotor position. Thus, the torque generated by the 10 motor in the said scenario will be 0 as sin 0 is 0.
In Figure 1(c), the representation shows that the flux direction indicated by the encoder (?_rotor_offset) deviates at an angular difference of ?_offset, and notably, this deviation is exactly 90 degrees from the actual direction of the rotor flux (?_rotor_actual). As a result, the encoder (206) incorrectly estimates the rotor 15 position, introducing a significant angular offset. In this specific scenario, the current supplied to the stator is aligned at an angle of 180 degrees concerning the actual rotor position. This alignment implies that the current is supplied in the same direction as the actual rotor flux. In terms of the torque equation, this configuration results in an angular difference (?) of 180 degrees, thus the torque generated by the 20 motor is zero as sine 180=0.
[00031]
Figure 2 illustrates a system of calibrating an offset angle of a motor (200) as per an embodiment of the present invention. As per an embodiment of the present invention, a system of calibrating an offset angle of a motor (200) sometimes referred as a system (200), comprises a control unit (204). The control unit (204) is 25 communicably connected to the motor unit (202). As per an embodiment of the present invention, the motor unit (202) is a delta motor which comprises three phases (U, V, W). In a delta-connected three-phase motor, each of the three motor winding phases is connected in a closed-loop or triangular configuration, where a starting point of one winding is connected to the finishing point of the next winding 30
11
and so on, forming a continuous loop.
As per an embodiment of the present invention, the delta motor is converted into a start motor as delta motors does not have a neutral point. In a star-connected three-phase motor, each of the three motor winding phases (U, V, W) is connected to a common point or neutral point (N) forming a star-shaped pattern. One end of each winding is connected to the common 5 neutral point, and the other ends are the motor terminals. The system also includes an encoder (206) which is connected to the control unit (204).
[00032]
Figure 3 and Figure 4 illustrate a graphical representation of the recorded back emf of the motor unit (202) as per an embodiment of the present invention. Figure 5 illustrates a graphical representation denoised back emf of the motor unit 10 (202) as per an embodiment of the present invention. Figure 6 illustrates a graphical representation of the denoised back emf of the motor unit (202) and corresponding encoder (206) angle as per an embodiment of the present invention. For the sake of brevity and comprehensive explanation of the present invention, the figure 3, the figure 4, the figure 5, and the figure 6 are explained together. As per an embodiment 15 of the present invention, the motor unit (202) is operated in a load condition, whereby the motor unit (202) is communicably connected the control unit (204). To determine an offset angle of a motor unit, the motor unit (202) is operated at a predefined revolutions per minute (RPM) by supplying power to the motor unit. For example, the motor unit (202) operated at an RPM range from 1000 RPM-7000 20 RPM. After operating the motor unit (202) operated at the predefined RPM, the supply of power is stopped, which causes the motor unit (202) to deaccelerate gradually. For instance, consider that the motor unit (202) is operated at a 2000 RPM by supplying power input, and then the supply of power is stopped to the motor unit, which causes the motor unit (202) to deaccelerate gradually. The control 25 unit (204) is configured to record, a back EMF voltage of the motor unit (202) while the motor unit (202) is deaccelerating. As evident from Figure 3 and Figure 4, since, the motor unit (202) is in a loaded condition, the back emf generated by the motor unit (202) includes numerous noises. Further, as evident from Figure 3, since the motor unit (202) is decelerating, therefore there is a significant amplitude difference 30 (d) between the between plurality of cycles (302a, 302b, 302c, 302d) of the back
12
emf wavelength. Thus, keep in view the noise and the uneven amplitude difference
between the peaks of the plurality of cycles (302a, 302b, 302c, 302d) of the back emf wavelength, it is important to denoise the recorded back EMF voltage of the motor unit. Therefore, the recorded back EMF (302) is denoised by one or more denoising method. As per an embodiment of the present invention, referring figure 5 4, the recorded back EMF (302) is denoised using wavelet denoising method. The wavelet denoising is a signal processing technique that utilizes wavelet transforms to reduce noise or unwanted disturbances from a signal while preserving important features. Thus, graphical representation of the denoised recorded back EMF (602) is shown in Figure 6. The amplitude of the cycles of the denoised recorded back 10 EMF (602) is uneven as the motor unit (202) is gradually deaccelerating and approaching 0 RPM in a time window ranging from T=1 to i. The Figure 6 also demonstrates corresponding angular position (604) of the encoder (206) at the respective time window ranging from T=1 to i.
[00033]
Figure 7(a) and Figure 7(b) illustrate a graphical representation of the 15 offset angle calibration method for the recorded back emf of the motor unit (202) as per an embodiment of the present invention. Figure 8 illustrates a flow chart for determining an offset angle of a motor unit (202) as per an embodiment of the present invention. Figure 9(a) and Figure 9(b) illustrate a flow chart for executing an offset angle calibration method as per an embodiment of the present invention. 20
[00034]
For determining the offset angle of a motor unit, the motor unit (202) is operated at a predefined RPM, and then the power supply to the motor unit (202) is stopped to deaccelerate the motor unit (202) at step 802. While the motor unit (202) is deaccelerating, the control unit (204) records the back emf generated by the motor unit (202) at step 804. As the motor unit (202) is communicably coupled with the 25 control unit (204) , the recorded back EMF includes numerous noises. Thus, to determine the offset value of the motor unit, the recorded back emf is denoised at step 806. Once, the recorded back emf is denoised the control unit (204) executes the offset angle calibration method at step 808 to accurately determine the offset angle of the motor unit. 30
13
[00035]
For offset angle calibration, a set of data relating a denoised back EMF voltage value corresponding to a time window ranging from 1 to i is recorded at step 902 by a control unit (204). For example, consider that the denoised back emf voltage is recorded for time window ranging from 1 to 5 as shown in Fig. 7(a). At step 904, at least one of the set of data corresponding to a predefined time window 5 j is compared with data of remaining time window i-j. For example, the predefined time window is when t=2. The data as time window 2 is compared with the remaining time windows at step 904. If the data at the predefined time window is highest among the remaining time windows at step 916, then corresponding or respective encoder (206) angle value is recorded and corresponding mechanical 10 angular value and electrical angular value is calculated at step 918. However, if the data at the first-time window is the highest value, at step 912, then control unit (204) will initiate the offset angle calibration at the next positive cycle of the denoised back emf at step 914. Importantly, the data at the first-time window is highest means that the highest value of the back emf has already crossed before the initiation of 15 the offset angle calibration method by the control unit (204) . Thus, it is important to wait for the next positive cycle of the back emf. However, if the data at the kth position of the time window is highest at step 908, then the offset angle calibration method is reiterated wherein the predefined time window j is reset to kth time window. For example, as shown in fig. 7(a), at time window 701 ranging from 1 to 20 5, the data at time window 2 is compared with the rest of data in the remaining time window. If the data at time window 4 is highest, the offset angle calibration method is reiterated with a new time window at 702. The new time window 2 is set at the time window 4 of the time window 701. Subsequently, the data at the new time window 2 is compared with the rest of the time window, wherein the data at time 25 window 5 is highest. Further, a third time window is reiterated at 703 whereby the time window 2 is started at highest time window 5. The process of reiterating the offset angle calibration method is continue till the data at the time window 2 is highest. After collecting n number of samples at step 920, a mean value of all the collected samples is calculated to determine the appropriate offset angle value at 30 step 922.
14
[00036]
The present invention advantageously provides an offset angle calibration method and a system, which eliminates need for physically aligning the encoder (206) unit at a specific angle with the motor shaft. Thus, the present invention provides a time efficient method a and a system to calibrate an offset angle of a motor unit (202) efficiently. 5
[00037]
Further advantageously, the present invention eliminates the necessity of an auxiliary motor for measuring the offset angle of each primary motor. Importantly, the present invention eliminates complexity of individual mechanical linking of the primary motors to the auxiliary motor through nuts and bolts, thereby providing a simple, cost efficient and time efficient method and a system to calibrate 10 an offset angle of the motor unit.
[00038]
In light of the above-mentioned advantages and the technical advancements provided by the disclosed method and system, the claimed steps as discussed above are not routine, conventional, or well understood in the art, as the claimed steps enable the following solutions to the existing problems in 15 conventional technologies. Further, the claimed steps clearly bring an improvement in the functioning of the system of calibrating an offset angle of the motor itself as the claimed steps and constructional features provide a technical solution to a technical problem.
[00039]
Finally, the language used in the specification has been principally selected 20 for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter and is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not 25 limiting, of the scope of the invention, which is set forth in the following claims.
[00040]
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are
15
not intended to be limiting, with the true scope and spirit being indicated by the
following claims.
[00041]
A person with ordinary skills in the art will appreciate that the systems, modules, and sub-modules have been illustrated and explained to serve as examples and should not be considered limiting in any manner. It will be further appreciated 5 that the variants of the above disclosed system elements, modules, and other features and functions, or alternatives thereof, may be combined to create other different systems or applications.
[00042]
Those skilled in the art will appreciate that any of the aforementioned steps and/or system modules may be suitably replaced, reordered, or removed, and 10 additional steps and/or system modules may be inserted, depending on the needs of a particular application. In addition, the systems of the aforementioned embodiments may be implemented using a wide variety of suitable processes and system modules, and are not limited to any particular computer hardware, software, middleware, firmware, microcode, and the like. The claims can encompass 15 embodiments for hardware and software, or a combination thereof.
[00043]
While the present disclosure has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a 20 particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, it is intended that the present disclosure is not limited to the particular embodiment disclosed, but that the present disclosure will include all embodiments falling within the scope of the appended claims. , C , Claims:I/We claim:
1.
A method of determining an offset angle of a motor unit, the method comprises the steps of:
deaccelerating (802), the motor unit (202) after operating the motor 5 unit (202) at a predefined revolution per minute (RPM);
recording (804), by a control unit (204) a back EMF voltage of the motor unit (202) while the motor unit (202) is deaccelerating;
and
executing (808), by the control unit (204) an offset angle calibration 10 method (900).
2.
The method of determining the offset angle of a motor unit (202) as claimed in claim 1, wherein the offset angle calibration method (900) comprises the steps of: 15
recording (902), by the control unit (204) a set of data relating the denoised back EMF voltage value corresponding to a time window ranging from 1 to i;
comparing (904), by the control unit (204) at least one of the set of data corresponding to a predefined time window j with remaining 20 set of data in time window i-j,
if the value of the at least one of the set of data corresponding to the predefined time window is higher than the remaining set of data in time window i-j, (916) estimating the corresponding angular position of an encoder (206) (918); 25
else, if the voltage value of back emf at a time window k is highest, whereby if the time window k is less than or equal to i, and more than 1 the predefined time window j is reset to a time window k and the offset angle calibration method (900) is reiterated (908).
30
17
3.
The method of determining the offset angle of a motor unit (202) as claimed in claim 1, denoising (806), by the control unit (204) the recorded back EMF voltage values (612) of the motor unit (202) before executing the offset angle calibration method.
5
4.
The method of determining the offset angle of a motor unit (202) as claimed in claim 1, wherein if the time window k is equal to 1, the offset angle calibration method (900) is iterated in a subsequent positive cycle of back emf back EMF voltage value of the motor unit.
10
5.
The method of determining the offset angle of a motor unit (202) as claimed in claim 1, wherein estimating the corresponding angular position of an encoder (206) is converted into an electrical angle to estimate the offset angle of a motor unit.
15
6.
The method of determining the offset angle of a motor unit (202) as claimed in claim 1, wherein the control unit (204) is configured to record a set of data corresponding to angular position of an encoder (206) by the offset angle calibration method (900) till the RPM of the motor unit (202) is zero, and wherein the offset angle is determined by calculating a mean value of 20 set of data at step (922) corresponding to the angular position of the encoder (206).
7.
An offset angle calibration method (900), wherein the offset angle calibration method (900) comprises the steps of: 25
recording (902), by a control unit (204), a set of data relating a denoised back EMF voltage (612) corresponding to a time window ranging from 1 to i;
comparing (904), by the control unit (204), at least one of the set of data corresponding to a predefined time window j with remaining 30 set of data in time window i-j,
18
if the value of the at least one of the set of data corresponding to the predefined time window is highest than the remaining set of data in time window i-j, estimating a corresponding angular position of an encoder (206) (918);
else, if the voltage value of back emf at a time window k is 5 highest, whereby if the time window k is less than or equal to i, and more than 1 the predefined time window j is reset to a time window k and the offset angle calibration method (900) is reiterated (910).
8.
The offset angle calibration method (900), as claimed in claim 5, wherein if 10 the time window k is equal to 1, the offset angle calibration method (900) is iterated in a subsequent positive cycle of back emf back EMF voltage value of the motor unit (914) by the control unit (204).
9.
The offset angle calibration method, as claimed in claim 5, wherein 15 estimating the corresponding angular position of an encoder (206) is converted into an electrical angle to estimate the offset angle of a motor unit (918) by the control unit (204).
10.
The offset angle calibration method, as claimed in claim 5, wherein a set of 20 data corresponding to angular position of an encoder (206) is recorded by the offset angle calibration method (900) till the RPM of the motor unit (202) is zero and wherein the offset angle is determined by calculating an mean value of set of data corresponding to the angular position of the encoder (206) at step (922). 25
11.
A system of calibrating an offset angle of a motor (200), wherein the system (200) comprises a control unit (204), the control unit (204) is communicably connected to a motor unit (202), the control unit (204) is configured to:
record (804), a set of data relating a denoised back EMF voltage 30 value corresponding to a time window ranging from 1 to i;
19
compare (904), at least one of the set of data corresponding to a predefined time window j with remaining set of data in time window i-j,
if the value of the at least one of the set of data corresponding to the predefined time window is highest than the remaining set of data in time window i-j, estimate the corresponding angular position 5 of an encoder (206) (910);
else, if the voltage value of back emf at a time window k is highest, whereby if the time window k is less than or equal to i, and more than 1 the predefined time window j is reset to a time window k and reiterate the offset angle calibration method (910). 10
12.
The system of calibrating the offset angle of the motor (200), as claimed in claim 9, wherein if the time window k is equal to 1, the offset angle calibration method (900) is iterated in a subsequent positive cycle of back emf back EMF voltage value of the motor unit (914). 15
13.
The system of calibrating the offset angle of the motor, as claimed in claim 9, wherein estimating the corresponding angular position of an encoder (206) is converted into an electrical angle to estimate the offset angle of a motor unit (918). 20
14.
The system of calibrating the offset angle of the motor (200), as claimed in claim 9, wherein a set of data corresponding to angular position of an encoder (206) is recorded by the offset angle calibration method (900) till the RPM of the motor unit (202) is zero and wherein the offset angle is 25 determined by calculating an average value of set of data corresponding to the angular position of the encoder (206) (922).
15.
A system of calibrating an offset angle of a motor (200), the system (200) comprising: 30
20
a motor unit (202), wherein the motor unit is configured to have a star configuration, wherein the star configuration comprises a neutral point (N);
a control unit (204), the control unit (204) is communicably connected to the neutral point (N); 5
an encoder (206), the encoder (206) is communicably connected to the control unit (204).