Device including motor, inverter drive device and controller, and electric vehicle including the device

Abstract

To provide an apparatus comprising a motor, an inverter drive, and a controller suitable for use in an electric vehicle, in which a processing of a calculation and a signal input required for a FOC is performed more quickly.SOLUTION: An apparatus according to the invention comprises: a motor, an inverter drive for the motor; and a controller for the motor. The motor comprises a rotor having an output shaft and a stator having a plurality of windings. The inverter drive device includes a gate high side driver and a gate low side driver for each winding. The controller includes a microcontroller and a plurality of pulse width modulators. The apparatus has one pulse width modulator for each gate high side driver and each gate low side driver, the microcontroller is programmed to generate a PWM signal for the gate driver, and the PWM signal represents a required torque.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a motor, and more particularly to a controller for a drive motor of an electric vehicle. [Background technology]

[0002] Electric vehicles typically use field-oriented control (FOC) to control the motor used to propel the vehicle. FOC is preferred over other forms of motor control because it provides the smoothest and most accurate motor control. However, FOC requires a large amount of processing power due to its complexity. FOC works by mathematically transforming the motor's electrical equations into a rotating reference frame with d- and q-axes that are 90 degrees out of phase. The motor's torque is controlled by the d-axis current, and the motor's speed is controlled by the q-axis current. The controller uses the motor's speed, torque, and other parameters to calculate the d- and q-axis currents. Motor control is achieved by the switching circuitry of the motor inverter. Not only are FOC's processing requirements high, but the speed and position information about the rotor must be very accurate, necessitating the use of specialized sensors called resolvers.

[0003] FOC provides the smoothest and most accurate control, but is limited in maximum switching speed by the time lag between getting data from the resolver and reading that data into the controller.

[0004] Another known method of controlling a motor is known as direct torque control (DTC). While DTC is a much simpler control configuration than FOC, DTC is not typically used in traction control applications because the estimation errors used in DTC cause torque ripple. This torque ripple results in an insufficient level of vehicle control. The motor output torque is not smooth, resulting in uneven vehicle acceleration. Importantly, this can lead to unintended vehicle acceleration, driveline vibration, and noise. Torque ripple has been considered an inherent limitation of direct torque control. DTC is typically used only in applications where highly accurate control of motor torque and speed is not required.

[0005] With the development of electric vehicles, there is an increasing demand for electric motors that can run at higher speeds, as increasing motor speeds increases power density, and there is also a demand to reduce the cost of motors and their control systems.

[0006] The limiting factor for motors using FOC is the calculations required for FOC and the time it takes to process resolver sensor inputs. Summary of the Invention [Problem to be solved by the invention]

[0007] It would be desirable to provide a motor controller suitable for use in electric vehicles in which these calculations and signal processing can be performed more quickly.

[0008] It has been discovered that improved control of a motor can be achieved by providing the motor with a torque sensor configured to sense the torque output of the motor.

[0009] A known type of sensor that can sense torque is a SAW sensor (surface acoustic wave), which is described in the applicant's UK patent no. GB2397379. [Means for solving the problem]

[0010] According to a first aspect of the present invention, there is provided an apparatus including a motor, an inverter drive device for the motor, and a controller for the motor. The motor includes a rotor having an output shaft and a stator having a plurality of windings. The inverter driver has a gate high-side driver and a gate low-side driver for each winding. The controller includes a microcontroller and multiple pulse width modulators, one for each high-side gate driver and one for each low-side gate driver, and is programmed to generate PWM signals for the gate drivers, the programmed PWM signals representing the desired torque. The microcontroller is connectable to a communication network. The motor includes a torque sensor, which is a SAW (surface acoustic wave) sensor system, one part of which is mounted on the rotor and another part of which is mounted on the stator, and an electrical output signal of the SAW sensor system, which represents the actual motor torque, forms an input to the microcontroller. The electrical output signal of the SAW sensor system is compared with the demanded torque by a microcontroller, and the PWM signal for the gate driver is modified by the microcontroller according to the difference between the programmed PWM signal representing the demanded torque and the actual motor torque represented by the electrical output signal of the SAW sensor system.

[0011] By sensing the actual motor torque and using it to modify the PWM signal to the gate drivers, the torque estimation calculations of prior art control systems are no longer required. Measuring the actual torque eliminates the need for lookup table-based calculations used to generate torque estimates.

[0012] The torque sensor may be positioned to sense torque on the output shaft. The portion of the SAW sensor system mounted on the rotor may be mounted on the output shaft.

[0013] The motor may be a three-phase motor, and the plurality of windings includes three phase windings.

[0014] The apparatus further includes a motor speed sensor and / or a motor temperature sensor that generates a signal indicative of the motor speed sensor and / or the motor temperature sensor, the output of each motor speed sensor and / or the motor temperature sensor being connected to and forming an input to a microcontroller, the microcontroller being programmed to generate a PWM signal for the gate driver based on the sensed speed and / or the sensed temperature.

[0015] The motor temperature sensor may be configured to sense the temperature within the stator.

[0016] The motor temperature sensor may be configured to sense the temperature within the windings of the stator.

[0017] The apparatus may further comprise a phase current sensor having an output, the output of the phase current sensor being connected to and forming an input to the microcontroller.

[0018] The microcontroller may be configured to generate a field weakening current signal based on the output of the phase current sensors.

[0019] The communication network may be a CANbus.

[0020] The portion of the SAW sensor system attached to the rotor is the rotor coupler, and the other portion attached to the stator is the stator coupler. Each coupler contains a near-field antenna.

[0021] The apparatus may further comprise at least one sensor electrically connected to the near-field antenna of the rotor coupler.

[0022] The rotor may include at least one flat surface, and the at least one sensor is mounted to the at least one flat surface.

[0023] The rotor may include two flat surfaces 180° apart, each of the flat surfaces having at least one sensor mounted thereon.

[0024] The near field antenna of the stator coupler may be electrically connected to an interrogation unit.

[0025] The interrogation unit may include an application specific integrated circuit (ASIC).

[0026] The interrogation unit, for example an ASIC thereof, may generate a radio frequency interrogation signal having a range of frequencies. The frequency range may be 420 to 440 MHz.

[0027] One of the sensors may be configured to pick up radio frequency signals in a first portion of a frequency range. The other of the sensors may be configured to pick up radio frequency signals in a second portion of the frequency range. The first part of the frequency range is 420-430 MHz, and the second part of the frequency range is 430-440 MHz.

[0028] The backscattered signal from the at least one sensor may be reflected by the near field antenna back to the interrogation unit, eg, its ASIC, and read by the interrogation unit, eg, ASIC.

[0029] The output signal from the interrogation unit, typically an ASIC, forms the input to a microcontroller, thus enabling control of the motor according to the torque sensed at the motor, typically the output shaft of the motor.

[0030] According to a second aspect of the present invention, there is provided an electric vehicle comprising at least one device according to the first aspect of the present invention. [Brief explanation of the drawings]

[0031] The drawings illustrate prior art examples of motors and associated controls, as well as motors and associated controls of the present invention, and are as follows, by way of example: [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a prior art FOC motor control configuration. [Figure 2] 1 is a schematic diagram of an example of a motor control device according to the present invention; [Figure 3] 1 is a schematic diagram of a motor according to the present invention; [Figure 4a] FIG. 4 is a schematic diagram of the assembled motor shown in FIG. 3. [Figure 4b] FIG. 4 is an exploded view of the motor shown in FIG. 3. [Figure 5] FIG. 5 is an exploded view of a SAW sensor assembly of the motor shown in FIGS. 3 to 4b. DETAILED DESCRIPTION OF THE INVENTION

[0032] Referring first to FIG. 1, a three-phase motor 1 includes three sets of phase windings: A phase, B phase, and C phase.

[0033] The motor 1 is driven by an inverter 2 consisting of high-side gate drivers GHA, GHB, and GHC and low-side gate drivers GLA, GLB, and GLC.

[0034] An input voltage (B+ B-) is applied across the inverter and the input current is sensed by current sensor CS1.

[0035] Each set of windings is provided with a current sensor, current sensor A (CSA), current sensor B (CSB), and current sensor C (CSC), and each current sensor senses the current in the winding A to C to which the current sensor CSA to CSC is assigned.

[0036] The inverter controller 3 includes a microcontroller 4 and two sets of three pulse width modulators 5a and 5b. Each pulse width modulator in the set of three pulse width modulators 5a is connected to a respective one of the high-side gate drivers GHA, GHB, and GHC. Similarly, each pulse width modulator in the set of three pulse width modulators 5b is connected to a respective one of the low-side gate drivers GLA, GLB, and GLC.

[0037] The microcontroller 4 is also connected to an external communication network, such as the CANbus of the vehicle of which the motor 1 forms part. Current sensors CS1, CSA, CSB and CSC are also connected to the microcontroller 4 and provide inputs thereto.

[0038] The motor 1 is provided with a temperature sensor in the form of a thermistor arranged to sense the temperature of one or more of the phase windings A to C. The output of the thermistor is connected to the microcontroller 4 as an input thereto.

[0039] Motor 1 also includes a sine encoder that provides sine and cosine signals as the rotor (not shown) of motor 1 rotates. The sine and cosine signals provide an indication of rotor position at any instant. The sine and cosine signals are provided as inputs 9 to microcontroller 4 and are used to calculate motor speed and estimate rotor position.

[0040] In use, when the driver of the vehicle of which the motor 1 forms part issues a command, for example by pressing the accelerator pedal, the speed / torque request is sent over the CANbus 6 to the microcontroller 4 .

[0041] The sine and cosine signals from the encoder are fed to a microcontroller 4, which calculates the motor speed and estimates the rotor position.

[0042] The currents sensed by CS1, CSA, CSB, and CSC are provided to microcontroller 4 as current sense inputs 7. Microcontroller 4 is programmed with an algorithm such as Clarke or Park transform whereby a torque estimate is derived from the inputs to microcontroller 4.

[0043] The microcontroller 4 calculates the pulse width modulated switching of the gate drivers GHA, GHB, GHC and GLA, GLB and GLC to precisely adjust the current flowing into and out of the motor 1 to achieve the desired output shaft speed and torque.

[0044] If additional field weakening is required, the microcontroller must also be able to calculate and generate the appropriate secondary stator current.

[0045] In Figures 1 and 2, like numbers are used to indicate like parts.

[0046] FIG. 2 shows a motor and motor controller of the present invention having direct torque control with active torque feedback to an inverter, which includes a three-phase motor 1 having three sets of phase windings, phase A, phase B and phase C.

[0047] The motor 1 is driven by an inverter 2 consisting of high-side gate drivers (GHA, GHB, GHC) and low-side gate drivers GLA, GLB, GLC.

[0048] An input voltage (B+ B-) is applied across the inverter and the input current is sensed by current sensor CS1.

[0049] The phase A winding set is shown as including current sensor A (CSA), although current sensor CSA is optional.

[0050] The inverter controller 3 includes a microcontroller 4 and two sets of three pulse-width modulators 5a and 5b. Each pulse-width modulator in the set of three pulse-width modulators 5a is connected to a respective one of the gate high-side drivers GHA, GHB, and GHC. Similarly, each pulse-width modulator in the set of three pulse-width modulators 5b is connected to a respective one of the gate low-side drivers GLA, GLB, and GLC.

[0051] The microcontroller 4 is also connected to an external communication network, such as the CANbus of the vehicle of which the motor 1 forms part. The current sensors CS1 and, if present, CSA, are also connected to the microcontroller 4 and provide inputs thereto.

[0052] The motor 1 is provided with at least one temperature sensor in the form of a thermistor or thermistors arranged to sense the temperature of one or more of the phase windings A to C. The thermistor output 8 is connected to the microcontroller 4 as an input thereto.

[0053] The motor 1 also includes a speed sensor which measures the rotational speed of the motor 1 and provides a motor speed input signal 10 to the microcontroller 4 .

[0054] The motor 1 is also provided with a torque sensor TS1 which measures the torque on the output shaft 1' of the motor 1. The torque sensor is, for example, a SAW (Surface Acoustic Wave) sensor system of the type described in GB Patent No. 2397379.

[0055] In use, when the driver of the vehicle of which the motor 1 forms part gives a command, for example by pressing the accelerator pedal, the speed / torque request is sent by CANbus 6 to the microcontroller 4. The microcontroller is initially programmed to follow the command, such as accelerator pedal position, and generate a PWM signal (pulse width modulated signal) for the gate driver of the inverter 2.

[0056] The signal 10 from the motor speed sensor is compared to the speed request sent to the gate drivers of the inverter 2 .

[0057] Similarly, the signal 11 from the output shaft torque sensor TS1 is compared to the torque demand communicated to the inverter 2 gate driver.

[0058] The microcontroller 4 calculates the difference between the speed demand and the measured motor speed, and the difference between the torque demand and the torque measured in the output shaft 1', and uses these calculated differences to calculate the PWM required by the gate drivers to cause the currents to flow to and from the phase windings of the motor to cause the motor to run at the desired speed with the desired output shaft torque.

[0059] If additional field weakening is required, the microcontroller can also calculate and generate the appropriate secondary stator current. Phase current sensor A provides a signal that allows the field weakening current to be calculated.

[0060] 3 and 4a, the motor 1 includes a motor frame 1a, a stator 1b, a rotor 1c, an output shaft 1d, end plates 1e, and support bearings 1f that support each end of the output shaft 1d. A SAW (surface acoustic wave) sensor assembly 20 is attached to the output shaft 1d.

[0061] 4a and 5 show the SAW sensor assembly 20 in more detail. The SAW sensor assembly 20 comprises a (PCB) stator coupler 21 including a collar 21a, typically formed from glass-reinforced plastic. The collar 21a carries an outer conductive layer forming a ground plane antenna 21b and an inner conductive track forming a near-field antenna 21c. Typically, the conductive components are formed from copper, although any suitable conductor can be used. The SAW sensor assembly 20 further comprises a printed circuit board (PCB) rotor coupler 22, which includes a collar 22a, typically formed from glass-reinforced plastic. The collar 22a carries an outer conductive layer track forming a near-field antenna 22b.

[0062] The stator and rotor couplers are separated by a small distance, typically between 1 mm and 20 mm.

[0063] The rotor coupler 22 is fixed to a rotor coupler mounting area 1d" of the output shaft 1d, for example, by adhesive. In the illustrated example, the rotor coupler mounting area 1d" is cylindrical. The output shaft 1d is provided with a sensor mounting area 1d', which has flat surfaces 23a and 23b facing each other on the shaft 1d. A high-frequency sensor 24a is mounted on the flat surface 23a, and a low-frequency sensor 24b is mounted on the flat surface 23b. Mounting the two sensors opposite each other makes it possible to compensate for shaft bending. In the illustrated embodiment, the sensors 24a and 24b are all quartz-packaged sensors. They require no power other than the radio-frequency signals they transmit and receive. Such sensors are known in the prior art and therefore will not be described in detail.

[0064] Sensors 24a and 24b are electrically connected to near-field antenna 22b of rotor coupler 22. The conductive track forming near-field antenna 22b consists of two sections with a small gap between them. Each of sensors 24a and 24b is connected to both sections of the conductive track by a pair of wires 22c and 22c', respectively.

[0065] The near-field antenna 21c of the stator coupler 21 is configured to be electrically connected to an interrogation unit that includes an application-specific integrated circuit (ASIC). As can be seen in FIG. 5, the collar 21a of the stator coupler includes a hole 21d. A pair of wire end terminals are attached to each portion of the near-field antenna 21c through the hole 21d, one terminal connected to each end 21c', 21c" of the near-field antenna 21c. The stator coupler 21 is mounted to a stator coupler housing 25, which includes mounting members 25a each having a hole 25b for receiving a screw for attaching the stator coupler housing 25 to the motor end plate 1e. The stator coupler housing 25 also provides openings 25c through which wires can be passed that attach the near-field antenna 21c to the interrogation unit.

[0066] In use, the ASIC generates a radio frequency interrogation signal, which in this example has a frequency of 420-440 MHz. This signal is transmitted to the stator near-field antenna 21c and then from the stator near-field antenna 21c to the rotor near-field antenna 22b. This radio frequency signal is transmitted by electrical connection 22c from the rotor near-field antenna 22b to sensors 24a and 24b, with sensor 24a picking up signals in the 430-440 MHz range and sensor 24b picking up signals in the 420-430 MHz range. Sensors 24a and 24b generate backscattered signals that vary in response to torque on, for example, shaft 1d. The backscattered signals from sensors 24a and 24b are reflected by near-field antennas 22b and 21c back to the interrogation unit and read by the interrogation unit's ASIC. The output signal from the ASIC forms an input to the microcontroller 4 shown in FIG. 2, which can control the motor 1 according to the torque sensed at the output shaft 1d.

[0067] By providing SAW sensors that sense motor speed and output shaft torque, an encoder that produces a sine / cosine output is not required, and there is no need to perform Clarke or Park transforms to estimate the torque required by the FOC motor control.

[0068] With DTC motor control, torque estimation, which limits the applications in which a DTC motor can be used, is replaced with measured torque, allowing for more accurate motor control without torque ripple. [Explanation of symbols]

[0069] 1 motor, three-phase motor 1´ Output shaft, shaft 1a Motor frame 1b Stator 1c rotor 1d Output shaft, shaft 1d´ Sensor mounting area 1d" rotor coupler mounting area 1e Motor end plate, end plate 1f Support bearing 10 signals, signals from motor speed sensor, motor speed input signal 11 signal, signal from output shaft torque sensor TS1 2 inverters 20 SAW (surface acoustic wave) sensor assembly 21 Stator coupler 21a Color 21b Ground Plane Antenna 21c Stator near-field antenna, near-field antenna 21c´ End of near-field antenna 21c" End of near-field antenna 21d hole 22 Rotor Coupler 22a color 22b Rotor near-field antenna, near-field antenna 22c Wire, Electrical Connection 22c´ Wire 23a flat surface 23b flat surface 24a High frequency sensor, sensor 24b Low frequency sensor, sensor 25 Stator coupler housing 25a Mounting member 25b hole 25c opening 3 Inverter Controller 4 Microcontrollers 5a Three Pulse Width Modulators 5b Three Pulse Width Modulators 6 CANbus 7 Current Sense Inputs 8 Output

Claims

1. An apparatus including a motor, an inverter drive device for the motor, and a controller for the motor, the motor includes a rotor having an output shaft and a stator having a plurality of windings; the inverter drive device has a gate high-side driver and a gate low-side driver for each of the windings, the controller comprises a microcontroller and a plurality of pulse width modulators, one pulse width modulator for each gate high-side driver and each gate low-side driver, the microcontroller being programmed to generate PWM signals for the gate drivers, the programmed PWM signals representing a desired torque; the microcontroller is connectable to a communications network; the motor includes a torque sensor, the torque sensor being a SAW (surface acoustic wave) sensor system, one part of the SAW sensor system mounted on the rotor and another part on the stator, an electrical output signal of the SAW sensor system representing actual motor torque forming an input to the microcontroller; the electrical output signal of the SAW sensor system is compared by the microcontroller to a desired torque, and the PWM signal for the gate driver is modified by the microcontroller according to a difference between a programmed PWM signal representing the desired torque and the actual motor torque as represented by the electrical output signal of the SAW sensor system.

2. The apparatus of claim 1 , wherein the torque sensor is positioned to sense torque on the output shaft.

3. 2. The apparatus of claim 1, wherein the motor is a three-phase motor and the plurality of windings includes three phase windings.

4. 2. The apparatus of claim 1, further comprising a motor speed sensor and / or a motor temperature sensor generating a signal indicative of the motor speed sensor and / or the motor temperature sensor, the output of each of the motor speed sensor and / or the motor temperature sensor being connected to and forming an input to the microcontroller, the microcontroller being programmed to generate a PWM signal for the gate driver based on the sensed speed and / or the sensed temperature.

5. The apparatus of claim 4 , wherein the motor temperature sensor is configured to sense a temperature within the stator.

6. The apparatus of claim 5 , wherein the motor temperature sensor is configured to sense a temperature within a winding of the stator.

7. 10. The apparatus of claim 1, further comprising a phase current sensor having an output, the output of the phase current sensor being connected to and forming an input to the microcontroller.

8. The apparatus of claim 7 , wherein the microcontroller is configured to generate a field weakening current signal based on the output of the phase current sensors.

9. The apparatus of claim 1 , wherein the communication network is a CANbus.

10. 10. The apparatus of claim 1, wherein the SAW sensor system attached to the rotor is a rotor coupler and the other part attached to the stator is a stator coupler, each coupler including a near-field antenna.

11. The apparatus of claim 10 , further comprising at least one sensor electrically connected to the near-field antenna of the rotor coupler.

12. The apparatus of claim 11 , wherein the rotor includes at least one flat surface, and the at least one sensor is mounted to the at least one flat surface.

13. 13. The apparatus of claim 12, wherein the rotor includes two flat surfaces 180 degrees apart, each of the flat surfaces having the at least one sensor mounted thereon.

14. The apparatus of claim 10 , wherein the near field antenna of the stator coupler is electrically connected to an interrogation unit.

15. 15. The apparatus of claim 14, wherein the interrogation unit comprises an application specific integrated circuit (ASIC).

16. 16. The apparatus of claim 15, wherein the ASIC generates a radio frequency interrogation signal having a frequency range.

17. one of the sensors is configured to pick up the radio frequency signals in a first portion of the frequency range; 16. Apparatus according to claim 15 when dependent on claim 13, wherein the other of the sensors is configured to pick up the radio frequency signals in a second part of the frequency range.

18. 15. The apparatus of claim 14, wherein a backscattered signal from the at least one sensor is reflected by the near field antenna to the interrogation unit and read by the interrogation unit.

19. 20. The apparatus of claim 18, wherein an output signal from the interrogation unit is an output of the SAW sensor system and an input to the microcontroller.

20. An electric vehicle comprising at least one device including a motor, an inverter drive device for the motor, and a controller for the motor, the motor includes a rotor having an output shaft and a stator having a plurality of windings; the inverter drive device has a gate high-side driver and a gate low-side driver for each of the windings, the controller comprises a microcontroller and a plurality of pulse width modulators, one pulse width modulator for each gate high-side driver and each gate low-side driver, the microcontroller being programmed to generate PWM signals for the gate drivers, the programmed PWM signals representing a desired torque; the microcontroller is connectable to a communications network; the motor includes a torque sensor, the torque sensor being a SAW (surface acoustic wave) sensor system, one part of the SAW sensor system mounted on the rotor and another part on the stator, an electrical output signal of the SAW sensor system representing actual motor torque forming an input to the microcontroller; the electrical output signal of the SAW sensor system is compared by the microcontroller to a desired torque, and a PWM signal for the gate driver is modified by the microcontroller according to a difference between a programmed PWM signal representing the desired torque and an actual motor torque as represented by the electrical output signal of the SAW sensor system.

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