Claims:I/ We claim:
1. A single motor drive system (100) for a multi-purpose household appliance, the drive system comprising:
a Permanent Magnet Synchronous Motor (PMSM) to operate a drive train of the multi-purpose household appliance based on one or more operating modes of the multi-purpose household appliance;
a plurality of sensors (102) to detect current speed and current torque of the PMSM; and
a control unit (104) configured to:
receive current speed value and current torque value of the drive train from the plurality of sensors (102);
determine current operating mode of the multi-purpose household appliance;
determine predefined speed value and predefined torque value of the drive train for the determined operating mode;
identify a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode; and
adjust dynamically the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the PMSM.
2. The drive system as claimed in claim 1, wherein the one or more operating modes of the multi-purpose household appliance is one of: wet grinder mode and mixer grinder mode.
3. The drive system as claimed in claim 1, wherein the PMSM is provided with a stator (106) and a rotor (108).
4. The drive system as claimed in claim 3, wherein the rotor (108) is provided with a plurality of fixed magnets.
5. The drive system as claimed in claim 4, wherein the rotor (108) of the PMSM is coupled to the drive train via a shaft (122).
6. The drive system as claimed in claim 1, wherein the plurality of sensors (102) are communicatively coupled to the control unit (104).
7. The drive system as claimed in claim 2, wherein the predefined speed for the wet grinder mode is in the range from 110 RPM to 130 RPM, wherein the predefined torque output for the wet grinder mode is in the range from 4.5 Newton meter (Nm) to 6 Nm.
8. The drive system as claimed in claim 2, wherein the predefined speed for the mixer grinder mode is in the range from 10000 RPM to 13000 RPM, wherein the predefined torque output for the mixer grinder mode is in the range from 0.3 Nm to 0.5 Nm.
9. A method for operating a single motor drive system for a multi-purpose household appliance, the method comprising:
detecting, by a plurality of sensors communicatively coupled to a microcontroller, current speed value and current torque value of drive train of the single motor drive system;
receiving, by a control unit communicatively coupled to the microcontroller and the plurality of sensors, current speed value and current torque value of the drive train of the single motor drive system;
determining, by the control unit, current operating mode of the multi-purpose household appliance;
determining, by the control unit, predefined speed value and predefined torque value of the drive train for the determined operating mode;
identifying, by the control unit, a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode; and
adjusting dynamically, by the control unit, the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the single motor drive system.
10. The method as claimed in claim 9, wherein the single motor drive system implements a Permanent Magnet Synchronous Motor (PMSM).
11. The method as claimed in claim 9, wherein the one or more operating mode of the multi-purpose household application is one of: a wet grinder mode and a mixer grinder mode.
12. The method as claimed in claim 11, wherein the predefined speed for the wet grinder mode is in the range from 110 RPM to 130 RPM, wherein the predefined torque output for the wet grinder mode is in the range from 4.5 Nm to 6 Nm.
13. The method as claimed in claim 11, wherein the predefined speed for the mixer grinder mode is in the range from 10000 RPM to 13000 RPM, wherein the predefined torque output for the mixer grinder mode is in the range from 0.3 Nm to 0.5 Nm. , Description:A SINGLE MOTOR DRIVE SYSTEM FOR A MULTI-PURPOSE HOUSEHOLD APPLIANCE
FIELD OF THE INVENTION
[0001] The present invention relates to a multi-purpose household appliance. In particular, the present invention relates to a single motor drive system for the multi-purpose household appliance.
BACKGROUND OF THE INVENTION
[0002] Conventionally, tabletop wet grinder and mixer grinder are separate appliances and therefore each occupies separate space. Further, generally known mixer grinder and wet grinder use induction motor for their functionality which consumes more space and volume due to low torque per unit volume. Induction motors depends on induced currents on the rotor by the stator windings, to create rotor flux which then interacts with the rotating magnetic field produced in the stator. The speed of the rotating magnetic field depends the number of poles and this speed is called Synchronous Speed Ns. The rotor tries to align itself with the rotating magnetic field is not able to attain synchronous speed. The difference between synchronous speed (Ns) and rotor speed (Nr) is called as slip and current drawn is inversely proportional to slip. And this is why an induction motor should never stall as the current will be too high and it can damage itself and cause fire hazards. Furthermore, conventionally these appliances do not have any speed control option and operate on fixed speed. Additionally, drive train of these appliances generally do not have any inbuilt overload protection which is usually achieved with help of additional overload relay which adds up to the cost.
[0003] Conventionally magnet based motors run at constant speed at any load, when there is no limitation in the current (torque). But this cannot be exercised in the real world conditions because all components work with maximum limit which is needed to make sure the system never crosses. Accordingly, the power output of the motor is limited. When the motor reaches the limited power the motor falls out of sync from the rotating flux which will eventually make the motor stall. So to address this situation, a constant entity to make sure the rotor is always in sync with the rotating magnetic flux generated by energising the stator is needed. Traditionally to address the above limitations Analog Circuits are used, which makes the motor a very expensive choice to use, especially in using it in high speed application where the components which have such high response rates were not simply available or very expensive.
[0004] Thus, in view of the above, there is a need for a multi-purpose household appliance configured to provide function of wet grinder and mixer grinder and configured to operate at variable speed.
SUMMARY OF THE INVENTION
[0005] An embodiment of the present invention discloses a single motor drive system for a multi-purpose household appliance. The drive system includes a Permanent Magnet Synchronous Motor (PMSM) to operate a drive train of the multi-purpose household appliance based on one or more operating modes of the multi-purpose household appliance. The drive system also includes a plurality of sensors to detect current speed and current torque of the PMSM and a control unit. The control unit is configured to receive current speed value and current torque value of the drive train from the plurality of sensors and determine current operating mode of the multi-purpose household appliance. The control unit further determines predefined speed value and predefined torque value of the drive train for the determined operating mode and identifies a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode. The control unit also adjusts dynamically the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the PMSM.
[0006] In accordance with an embodiment of the present invention, the one or more operating modes of the multi-purpose household appliance is one of: wet grinder mode and mixer grinder mode.
[0007] In accordance with an embodiment of the present invention, the PMSM is provided with a stator and a rotor. Further, the rotor is provided with a plurality of fixed magnets. Furthermore, the rotor of the PMSM is coupled to the drive train via a shaft.
[0008] In accordance with an embodiment of the present invention, the plurality of sensors are communicatively coupled to the control unit.
[0009] In accordance with an embodiment of the present invention, the predefined speed for the wet grinder mode is in the range from 110 RPM to 130 RPM, wherein the predefined torque output for the wet grinder mode is in the range from 4.5 Nm to 6 Nm.
[0010] In accordance with an embodiment of the present invention, the predefined speed for the mixer grinder mode is in the range from 10000 RPM to 13000 RPM, wherein the predefined torque output for the mixer grinder mode is in the range from 0.3 Nm to 0.5 Nm.
[0011] In accordance with an embodiment of the present invention a method for operating a single motor drive system for a multi-purpose household appliance is disclosed. The method includes detecting, by a plurality of sensors communicatively coupled to a microcontroller, current speed value and current torque value of drive train of the single motor drive system and receiving, by a control unit communicatively coupled to the microcontroller and the plurality of sensors, current speed value and current torque value of the drive train of the single motor drive system. The method further includes determining, by the control unit, current operating mode of the multi-purpose household appliance, determining, by the control unit, predefined speed value and predefined torque value of the drive train for the determined operating mode and identifying, by the control unit, a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode. The method also includes adjusting dynamically, by the control unit, the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the single motor drive system.
[0012] In accordance with an embodiment of the present invention, the single motor drive system implements a Permanent Magnet Synchronous Motor (PMSM).
[0013] In accordance with an embodiment of the present invention, the one or more operating mode of the multi-purpose household application is one of: a wet grinder mode and a mixer grinder mode.
[0014] In accordance with an embodiment of the present invention, the predefined speed for the wet grinder mode is in the range from 110 RPM to 130 RPM, wherein the predefined torque output for the wet grinder mode is in the range from 4.5 Nm to 6 Nm
[0015] In accordance with an embodiment of the present invention, the predefined speed for the mixer grinder mode is in the range from 10000 RPM to 13000 RPM, wherein the predefined torque output for the mixer grinder mode is in the range from 0.3 Nm to 0.5 Nm.
[0016] Accordingly, the present invention provides the following effects or advantages. In the present invention the Permanent Magnet Synchronous Motor (PMSM) is used to drive electronics which is specially designed to optimize the system volume and efficiency. PMSM uses permanent magnet for constant flux density over the air gap and it enables very low cogging torque. The PMSM is superior in performance over conventional induction motor and having very high-power density with the help of permanent magnets. Permanent magnet provides constant flux over its entire operating range which helps to achieve flat torque curve.
BRIEF DESCRIPTION OF DRAWINGS
[0017] The following drawings are illustrative of preferred embodiments for enabling the present invention and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
[0018] Figure 1 (a) illustrates an exploded view of a single motor drive system for a multi-purpose household appliance in accordance with an embodiment of the present invention;
[0019] Figure 1 (b) illustrates a side view of the single motor drive system in accordance with an embodiment of the present invention;
[0020] Figure 1 (c) illustrates a bottom view of the single motor drive system in accordance with an embodiment of the present invention;
[0021] Figure 1 (d) illustrates a top view of the single motor drive system in accordance with an embodiment of the present invention; and
[0022] Figure 2 illustrates flowchart for a method for operating the single motor drive system in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF DRAWINGS
[0023] The following disclosure is provided in order to enable a person having ordinary skill in the art to practice the invention. Exemplary embodiments are provided only for illustrative purposes and various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For the purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[0024] Figure 1 (a) illustrates an exploded view of a single motor drive system 100 for a multi-purpose household appliance in accordance with an embodiment of the present invention. Further, figure 1 (b) illustrates a side view of the single motor drive system 100 in accordance with an embodiment of the present invention. Furthermore, figure 1 (c) illustrates a bottom view of the single motor drive system 100 in accordance with an embodiment of the present invention. Additionally, figure 1 (d) illustrates a top view of the single motor drive system 100 in accordance with an embodiment of the present invention. For the sake of brevity figures 1(a), 1(b), 1(c) and 1(d) have been discussed together in subsequent paragraphs.
[0025] The multi-purpose household appliance may be understood as a table top appliance. Further, the multi-purpose household appliance may be have plurality of operating modes depending on the purpose for which the appliance may be employed. In an exemplary embodiment of the present invention, the multi-purpose household appliance may have a wet grinder mode and the mixer grinder mode as operation modes. The different operating modes may require a drive train of the multi-purpose household appliance to operate at different speed value and torque value. In exemplary embodiments of the present invention, the single motor drive system 100 may be configured to provide desired speed and torque to the drive train of the multi-purpose household appliance based on the operating mode.
[0026] In an exemplary embodiment of the present invention, the single motor drive system 100 may include a Permanent Magnet Synchronous Motor (PMSM), a plurality of sensors 102 and a control unit 104. The PMSM, the plurality of sensors 102 and the control unit 104 may be communicatively coupled to a memory and a microcontroller of the single motor drive system 100. The memory may include a database. Further, the microcontroller may be configured to control the operations of the PMSM, the plurality of sensors 102 and the control unit 104.
[0027] In an embodiment of the present invention, the microcontroller and the memory may form a part of a chipset installed in the single motor drive system 100. In another embodiment of the present invention, the memory may be implemented as a static memory or a dynamic memory. In an example, the memory may be internal to the single motor drive system 100. In another example, the memory may be implemented as an external memory for the single motor drive system 100. The memory may be a cloud based storage or onsite based storage. Further, the microcontroller may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, or any devices that manipulate signals, based on operational instructions.
[0028] In an embodiment of the present invention, the PMSM may be formed of a rotor 108, a stator 106, a winding 110, plurality of fixed magnets and a shaft 122. The rotor 108, the stator 106, the winding 110, the plurality of fixed magnet and the shaft 122 may be assembled between a top cap 112 and a bottom cap 114, such that the top cap 112 and the bottom cap 114 may be coupled together via a plurality of fasteners 120. In an embodiment of the present invention, the PMSM may also include a rotor 108 magnet cap 116 to cover open surface of the assembly of plurality of fixed magnets and the rotor 108. In another embodiment of the present invention, the PMSM may include bearing 118s configured to facilitate seamless movement to the shaft 122 under impact of the stator 106 and the motor. Further, the plurality of sensors 102 and the control unit 104 may be assembled to the PMSM along the top cap 112.
[0029] It may be known to a person skilled in the art that the PMSM may be constructed using permanent magnets instead of conducting materials in the rotors. This will reduce the losses which are incurred in inducing currents in the rotor in the case of induction motors. Further, the use of magnets makes the rotor get locked to the rotating magnetic field in the rotor. Thus making sure that the rotor always spins at the synchronous speed. Furthermore, the PMSM due to its construction can handle constant torque through its operating region which gives an added controlling advantages. Additionally, as the rotor contains permanent magnets it is very important to know the position of the rotor to synchronise the rotor flux and the rotating magnetic flux produced in the stator. It necessary to do this, because the rotating flux creates alternating magnetic fields which if is not in sync with the rotor then the net magnetic field experienced by the rotor becomes zero and the rotor looses torque and eventually comes to stall position. The control unit is used to ensure that the rotor is always in sync with the rotating magnetic flux generated by energising the stator. The control unit constantly measures the angular position of the rotor and energizes the motor windings accordingly which makes sure that the rotating magnetic flux is always in sync with the rotor flux even when in, stall condition.
[0030] In an embodiment of the present invention, the rotor 108 of the PMSM may be coupled to the drive train via the shaft 122. Accordingly, the PMSM may be configured to operate the drive train of the multi-purpose household appliance based on one or more operating modes of the multi-purpose household appliance. Further, the plurality of sensors 102 may be configured to detect current speed value and current torque value of the PMSM. The current speed value and the current torque value may be understood as values of the speed and the torque of the drive train at a present instance of time.
[0031] In an embodiment of the present invention, the control unit 104 may be configured to receive current speed value and current torque value of the drive train from the plurality of sensors 102. Further, the control unit 104 may be configured to determine current operating mode of the multi-purpose household appliance. Additionally, the control unit 104 may determine predefined speed value and predefined torque value of the drive train for the determined operating mode. In an embodiment of the present invention, the predefined speed value and the predefined torque value corresponding to each operating mode may be stored in the memory. Further, the predefined speed value and the predefined torque value may be understood as desired value of speed and torque to achieve requisite functionality from the multi-purpose household appliance without power overhead.
[0032] In an exemplary embodiment of the present invention, the predefined speed for the wet grinder mode may be in the range from 110 RPM to 130 RPM. Further, the predefined torque output for the wet grinder mode may be in the range from 4.5 Nm to 6 Nm.
[0033] In another exemplary embodiment of the present invention, the predefined speed for the mixer grinder mode may be in the range from 10000 RPM to 13000 RPM. Further, the predefined torque output for the mixer grinder mode may be in the range from 0.3 Nm to 0.5 Nm.
[0034] In an embodiment of the present invention, the algorithms such as, Cascaded Proportional Integral and Derivative algorithm may be used for controlling operation of the PMSM in the present invention. In ideal scenarios, the PMSM’s speed may be the same when a specific voltage is applied but under practical environment the speed might drop a little when there is an increase in load. To overcome this obstacle the motor is provided with a corrected voltage to run at constant speed. The Cascaded Proportional Integral and Derivative algorithm address the above mentioned obstacle. In this algorithm the speed is regulated constantly by comparing it to the actual speed and by amplifying the error signal to correct the input parameters. It is called as a cascaded algorithm because two individual entities such as speed and torque is regulated and connected in cascade mode. During the Start and Stop State the Specific Motor Variables and Parameters are initialised and Specific motor type is enabled. During the running and idling state the System parameters are continuously watched, additionally the above mentioned Cascaded Proportional, Integral and differential algorithm runs during the Running state. It makes sure the required speed is always maintained no matter what the disturbances are. Initially the system will be in Idling State and when the start switch is pressed the initialisation happens in the start state and the system moves to the running state. In the running state the status of the switch and system variables like temperature, current, input voltage are continuously monitored. In the case Over Voltage, Under Voltage, Overload, Over Temperature or when the switch is turned off the system moves to the stopping state where the motor is De-Initialised and the moves to the idle state. In the case of error the system moves to the error state, the system will return to the Idling stage when the error is cleared and the cycle continues.
[0035] Further, the control unit 104 may identify a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode. The bias may be understood as a difference between the predefined speed value and the predefined torque value, and the current speed value and the current torque value. The bias may affect the performance of the multi-purpose household appliance in the operating mode. Next, the control unit 104 may adjust dynamically the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the PMSM.
[0036] In operation, a control unit 104 may receive current speed value and current torque value of the drive train from the plurality of sensors 102. The control unit 104 may additionally determine current operating mode of the multi-purpose household appliance. Further, the control unit 104 may determine predefined speed value and predefined torque value of the drive train for the determined operating mode. Next, the control unit 104 may identify a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode. Further, the control unit 104 may adjust dynamically the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the PMSM.
[0037] Figure 2 illustrates a flowchart for a method for operating the single motor drive system in accordance with an embodiment of the present invention. In an exemplary embodiment of the present invention, the single motor drive system may implement a Permanent Magnet Synchronous Motor (PMSM).
[0038] At step 202, current speed value and current torque value of drive train of the single motor drive system may be detected. In an exemplary embodiment of the present invention, the detection of the current torque value and the current speed value may be by the plurality of sensors communicatively coupled to the microcontroller.
[0039] Next, at step 204, the current speed value and current torque value of the drive train of the single motor drive system may be received by a control unit communicatively coupled to the microcontroller and the plurality of sensors. Further, at step 206, the control unit may determine current operating mode of the multi-purpose household appliance. In an exemplary embodiment of the present invention, the one or more operating mode of the multi-purpose household application may be a wet grinder mode or a mixer grinder mode.
[0040] Further, at step 208, the control unit may determine predefined speed value and predefined torque value of the drive train for the determined operating mode. Next, at step 210, a bias between the current speed value and the current torque value with respect to the predefined speed value and the predefined torque value for the drive train for the determined operating mode may be identified by the control unit.
[0041] At step 212, the control unit may dynamically adjust the speed value and the torque value of the drive train based on the identified bias for the determined operating mode of the multi-purpose household appliance by varying operation of the single motor drive system.
[0042] In an embodiment of the present invention, the predefined speed for the wet grinder mode may be in the range from 110 RPM to 130 RPM. Further, the predefined torque output for the wet grinder mode may be in the range from 4.5 Nm to 6 Nm.
[0043] In an embodiment of the present invention, the predefined speed for the mixer grinder mode may be in the range from 10000 RPM to 13000 RPM. Further, the predefined torque output for the mixer grinder mode may be in the range from 0.3 Nm to 0.5 Nm.
[0044] Accordingly, the present invention provides the following effects or advantages. The present invention provides single motor unit for tabletop wet grinder and mixer grinder for domestic application. Further, the present invention facilitates in smooth speed control for tabletop wet grinder and mixer grinder and precise overload protection with the help of drive electronics. Additionally, the PMSM optimizes the performance of the multi-purpose household appliance over wide range of speed and sinusoidal back emf (BEMF) ensures very less torque ripple and very low cogging torque. Further, the control unit ensures full protection over drive system. Thus, wet grinder and mixer grinder can be changes with help of changeover switch for change in operating mode, along with fool proof mechanism for human safety and equipment safety.
[0045] While the exemplary embodiments of the present invention are described and illustrated herein, it will be appreciated that they are merely illustrative. It will be understood by those skilled in the art that various modifications in form and detail may be made therein without departing from or offending the spirit and scope of the invention as defined by the appended claims.