Control device for electric machine and associated method, electric machine and motor vehicle
By detecting the vehicle's stationary state on the slope and adjusting the motor's command torque according to the motor's cooling fluid temperature and torque, the problem of phase overheating of the motor's motor is solved, and the safe operation and life of the motor are achieved.
Patent Information
- Application Number
- CN202380078203.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-10
- Filing Date
- 2023-10-20
- Publication Date
- 2025-06-27
AI Technical Summary
In electric or hybrid motor vehicles, when the vehicle is stationary on a slope, the phase of the motor is overheated, resulting in damage to the stator coil insulation and the motor overheating.
The motor command torque is adjusted to avoid phase overheating by detecting whether the vehicle is stationary and motionless on the slope, and the reference duration is determined based on the motor's cooling fluid temperature and the torque of the rotor shaft.
It effectively avoids motor phase overheating, extends the service life of the motor, and avoids space and wiring problems in installing additional temperature probes in the motor.
Smart Images
Figure CN120226258A_ABST
Abstract
Description
Field of the Invention
[0001] The present invention relates to the control of rotating electrical machines.
[0002] More specifically, the present invention relates to a control device for controlling an electric machine for propelling an electric or hybrid motor vehicle, an electric or hybrid motor vehicle including such a device, and a method of implementing such a device. Background Art
[0003] Electric or hybrid motor vehicles are equipped with a rotating propulsion electric machine.
[0004] The electric machine generates a magnetic field through stator coils, causing a rotor to rotate inside the stator, thereby generating a motor vehicle propulsion torque. These stator coils form the phases of the electric machine, and current flows through these stator coils.
[0005] Typically, the electric machine is of a multi-phase type, such as a three-phase type.
[0006] When the motor vehicle is being propelled, each phase of the electric machine is supplied with a stator current, each current having the same intensity, such that the phases are balanced.
[0007] Since the current flowing through each phase is the same, the heat build-up generated by the current flowing through each phase is the same, which means that only a single temperature probe is required to measure the temperature of the phase coils.
[0008] However, when the driver of the motor vehicle adjusts the torque transmitted by the rotating electric machine via the accelerator pedal so that the motor vehicle remains stationary on a slope, the stator current can be injected into only one phase or into multiple phases, which means that the intensity of the current flowing through each phase is different, and which means that the heat build-up generated by the current flowing through each phase is different.
[0009] Holding the vehicle on a slope requires a high-intensity stator current, thereby generating a large amount of heat build-up.
[0010] The heat generated by the flow of the high-intensity stator current does not dissipate quickly enough, which means that significant thermal stress is generated and phase overheating may occur.
[0011] Overheating of the phase may cause damage to the insulation of the stator coils and cause overheating of the electric machine.
[0012] It is known practice to employ two temperature probes, each positioned between two consecutive phases, in order to detect phase overheating and prevent damage to the insulation of the stator coils and prevent overheating of the electric machine.
[0013] However, installing two temperature probes in the electric machine requires creating space in the electric machine to accommodate each temperature probe and requires providing wiring to connect these probes.
[0014] Accordingly, all or some of the disadvantages associated with the use of temperature probes in an electric machine are addressed. SUMMARY OF THE INVENTION
[0015] In view of the foregoing, one subject of the present invention is a method for controlling an electric machine for propelling an electric or hybrid motor vehicle.
[0016] The method includes:
[0017] -a) detecting that the motor vehicle has come to a standstill on a slope,
[0018] -b) determining a reference duration based on the temperature of the cooling fluid of the electric machine and the torque applied to the rotor shaft of the electric machine when the motor vehicle is at a standstill on the slope,
[0019] -c) starting a timer when it is detected that the motor vehicle has come to a standstill on the slope,
[0020] -d) determining a command torque for commanding the electric machine based on a set torque and based on a comparison between the reference duration and the time elapsed since the timer was started when the motor vehicle is at a standstill on the slope, and
[0021] -e) commanding the electric machine based on the command torque.
[0022] Preferably, when the motor vehicle is not at a standstill on the slope or when the time elapsed since the timer was started is less than the reference duration, the command torque for commanding the electric machine is equal to the set torque.
[0023] Advantageously, detecting that the motor vehicle has come to a standstill on the slope includes comparing the torque applied to the rotor shaft of the electric machine with a first predetermined threshold and comparing the speed of the motor vehicle with a second predetermined threshold, and when the torque is higher than the first predetermined threshold and the speed is lower than the second predetermined threshold, the motor vehicle is at a standstill on the slope.
[0024] Preferably, step a) further includes initializing a variable representing the number of repetitions of steps b) to d), the variable being set to a predetermined initialization value, and when the time elapsed since the timer was started is greater than or equal to the reference duration, determining the command torque for commanding the electric machine includes:
[0025] - comparing the command torque with a predetermined detection torque,
[0026] - determining a first intermediate torque, which is equal to the predetermined detection torque when the command torque is lower than the predetermined detection torque, or which is equal to the command torque minus a first correction torque when the command torque is higher than the predetermined detection torque,
[0027] - Update the commanded torque for the first time such that the commanded torque is equal to the first intermediate torque,
[0028] - When commanding the electric machine based on the commanded torque equal to the first intermediate torque, compare the speed of the motor vehicle with a second predetermined threshold, and
[0029] If the speed of the motor vehicle is higher than the second predetermined threshold, the method further includes:
[0030] - If the speed of the motor vehicle is higher than the second predetermined threshold, determine a second intermediate torque that is equal to the commanded torque plus a second correction torque,
[0031] - Update the commanded torque for the second time such that the commanded torque is equal to the second intermediate torque,
[0032] - If the variable is equal to the initialization value, determine the number of repetitions of steps b) to e) based on the temperature of the cooling fluid of the electric machine and the time elapsed since the timer was started,
[0033] - Compare the value of the variable with the number of repetitions, and
[0034] - If the value of the variable is lower than the number of repetitions, increment the value of the variable and repeat steps b) to e).
[0035] Advantageously, if the value of the variable is higher than the number of repetitions, the method further includes activating the parking brake of the motor vehicle.
[0036] Preferably, if the speed of the motor vehicle is lower than the second predetermined threshold and the torque applied to the rotor shaft of the electric machine is higher than the first predetermined threshold, the commanded torque remains unchanged.
[0037] Another subject of the present invention is a control device for controlling an electric machine for propelling an electric or hybrid motor vehicle.
[0038] The device includes:
[0039] - Detection means configured to detect that the motor vehicle has come to a standstill on a slope,
[0040] - First determination means configured to determine a reference duration based on the temperature of the cooling fluid of the electric machine and the torque applied to the rotor shaft of the electric machine when the motor vehicle is at a standstill on a slope,
[0041] - A timer, the detection means being further configured to start the timer when it is detected that the motor vehicle has come to a standstill on a slope,
[0042] - A second determination device configured to determine a command torque for commanding the electric motor based on a set torque and based on a comparison between a reference duration and the time elapsed since the timer was started while the motor vehicle is stationary on a slope, and
[0043] - A command device configured to command the electric motor based on the command torque.
[0044] Advantageously, the first determination device includes a predefined table that correlates at least the reference duration with values of the temperature of the cooling fluid and values of the torque applied to the rotor shaft of the electric motor.
[0045] Another subject of the invention is a hybrid or electric motor vehicle that includes a propulsion electric motor and control means as defined above. Description of the Drawings
[0046] Other objects, features, and advantages of the invention will become apparent upon reading the following description given by way of non-limiting example only and with reference to the drawings, in which:
[0047] Figure 1 schematically shows an example of a motor vehicle according to the invention;
[0048] Figure 2 shows an exemplary manner of implementing the control means according to the invention; and
[0049] Figure 3 shows an example of a graph according to the invention that correlates the number of repetitions with temperature and duration. Detailed Description
[0050] Figure 1 shows the electric motor vehicle 1 that includes: a propulsion electric motor 2 that includes a rotor shaft 3; a gearbox 4 that is connected to the wheels 5 of the motor vehicle 1 and is driven by the electric motor 2; and a cooling system 5 that is used to cool the electric motor 2.
[0051] As a variant, the motor vehicle 1 is a hybrid motor vehicle that includes the electric motor 2.
[0052] The cooling system 5 injects a cooling fluid into the electric motor 2 and collects the cooling fluid that has been heated by the heat generated by the electric motor 2 in order to cool the electric motor 2.
[0053] The fluid includes, for example, oil.
[0054] The motor vehicle 1 further includes a control device 6 for controlling the electric machine 2, a torque estimation device 7, a speed sensor 8 for measuring the speed of the motor vehicle 1, a temperature sensor 9 for measuring the temperature of the cooling fluid, and an accelerator pedal 10 for delivering a set torque to the electric machine 2.
[0055] The torque estimation device 7 estimates the torque applied to the rotor shaft 3 based on the current injected into the electric machine 2.
[0056] The torque estimation device 7, the speed sensor 8, the temperature sensor 9, and the accelerator pedal 10 are connected to the control device 6.
[0057] The control device 6 transmits a command signal to the electric machine 2, which signal indicates the commanded torque, and the accelerator pedal 10 transmits a set signal to the control device 6, which signal indicates the set torque.
[0058] The control device 6 includes a detection device 11, a first determination device 12, a timer 13, a second determination device 14, and a command device 15.
[0059] The control device 6 further includes an implementation device for implementing the detection device 11, the first determination device 12, the timer 13, the second determination device 14, and the command device 15.
[0060] The implementation device includes, for example, a processing unit 16 that implements the detection device 11, the first determination device 12, the timer 13, the second determination device 14, and the command device 15.
[0061] Reference Figure 2 , which figure shows an exemplary manner of implementing the control device 6.
[0062] The commanded torque for commanding the electric machine 2 is determined by the second determination device 14 based on the set torque and based on a comparison between a reference duration and the time elapsed since the timer was started while the motor vehicle 1 is stationary on a slope, as explained below.
[0063] It is assumed that the command signal transmitted by the command device 15 is the same as the set signal.
[0064] During step 20, the detection device 11 detects whether the motor vehicle 1 has come to a standstill on a slope.
[0065] The detection device 11 compares the torque applied to the rotor shaft 3 of the electric machine 2 transmitted by the torque estimation device 7 with a first predetermined threshold, and compares the speed of the motor vehicle 1 transmitted by the speed sensor 8 with a second predetermined threshold.
[0066] The first predetermined threshold is, for example, equal to 150 Nm, and the second predetermined threshold is, for example, equal to 30 revolutions per minute.
[0067] The values of the first threshold and the second threshold depend on the type of the vehicle 1.
[0068] If the torque applied to the rotor shaft 3 is higher than the first predetermined threshold and the speed of the motor vehicle 1 is lower than the second predetermined threshold, it is considered that the motor vehicle 1 is stationary on the slope (step 21), and the method continues with step 22.
[0069] If not, it is considered that the motor vehicle 1 is not stationary on the slope, and the command device 15 is commanded to transmit a command signal identical to the set signal.
[0070] During step 22, the variable VAR stored in the memory 17 of the device 6 is set to an initialization value predetermined by the processing unit 16.
[0071] The value of the variable VAR is set to zero, for example.
[0072] Furthermore, the detection device 11 starts the timer 13.
[0073] During 23, the first determination device 12 determines a reference duration based on the temperature of the cooling fluid detected by the temperature sensor 9 and based on the torque applied to the rotor shaft 3 transmitted by the torque estimation device 7.
[0074] The first determination device 12 includes a predetermined table TAB that associates the reference duration with the value of the temperature of the cooling fluid and the value of the torque applied to the rotor shaft of the electric motor 2.
[0075] For example, the table TAB is determined empirically through testing.
[0076] As long as the timer 13 has not reached the reference duration (step 24), the command device 15 transmits a command signal identical to the set signal (step 25).
[0077] When the time elapsed since the start of the timer 13 is greater than or equal to the reference duration (step 24), the second determination device 14 compares the value of the command torque with the value of a predetermined detection torque (step 26) and determines a first intermediate torque.
[0078] If the value of the command torque is lower than the value of the predetermined detection torque (step 27), then during step 28, the second determination device 14 updates the value of the first intermediate torque to make it equal to the value of the detection torque, and then the method continues with step 29.
[0079] If the value of the command torque is higher than the value of the predetermined detection torque (step 27), then during step 30, the second determination device 14 determines that the value of the first intermediate torque is equal to the value of the command torque minus the value of a first correction torque.
[0080] The correction torque is for example equal to the torque deficit factor expressed in Newton / second multiplied by the duration depending on the type of the vehicle 1, and the torque deficit factor is for example equal to -50 Nm / s.
[0081] The deficit factor is determined empirically by subjecting the motor vehicle 1 to various tests on slopes of different gradients and with different masses of the motor vehicle 1.
[0082] The method proceeds to step 29.
[0083] During step 29, the second determination device 14 updates the value of the command torque to be equal to the value of the first intermediate torque, and the command device 15 transmits a command signal representing the updated command torque.
[0084] During step 31, the second determination device 14 compares the speed of the motor vehicle 1 transmitted by the speed sensor 8 with a second predetermined threshold.
[0085] If the speed of the motor vehicle 1 is lower than the second predetermined threshold (step 32), then during step 33, the second determination device 14 compares the value of the torque applied to the rotor shaft 3 transmitted by the torque estimation device 7 with a first predetermined threshold.
[0086] If the value of the torque applied to the rotor shaft 3 is lower than the first predetermined threshold (step 34), it is considered that the motor vehicle 1 is no longer stationary on the slope.
[0087] The method proceeds to step 20.
[0088] If the value of the torque applied to the rotor shaft 3 is higher than the first predetermined threshold (step 34), then during step 35, the command torque is maintained such that the command signal transmitted by the command device 15 remains unchanged, and the method proceeds to step 31.
[0089] If the speed of the motor vehicle 1 is higher than the second predetermined threshold (step 32), then the motor vehicle 1 is moving.
[0090] The value of the command torque is not sufficient to keep the motor vehicle 1 stationary on the slope, and the method proceeds to step 36.
[0091] During step 36, the second determination device 14 determines that the value of the second intermediate torque is equal to the command torque plus the second correction torque, and updates the value of the command torque to be equal to the value of the second intermediate torque.
[0092] The command device 15 transmits a command signal representing the updated command torque.
[0093] If the value of the variable is different from the initialization value (step 37), then the method proceeds to step 38.
[0094] If the value of the variable is equal to the initialization value (step 37), then during step 39, the second determination device 14 determines the value of the variable REP based on the temperature of the cooling fluid transmitted by the temperature sensor 9 and based on the time Tc elapsed since the timer 13 was started.
[0095] The second determination device 14 determines the value of the variable REP, for example, from the graph GRAPH, which includes curves associating the value of the variable REP with the time Tc, each curve corresponding to a different temperature of the cooling fluid.
[0096] The variable REP and the graph GRAPH are stored, for example, in the memory 17.
[0097] Then, the method continues with step 38.
[0098] Figure 3 shows an example of the graph GRAPH including three curves C1, C2, C3 associating the value of the variable REP with the time Tc.
[0099] The first curve C1 corresponds to the temperature T1 of the cooling fluid, the second curve C2 corresponds to the temperature T2 of the cooling fluid, and the third curve C3 corresponds to the temperature T3 of the cooling fluid, the temperatures T1, T2, T3 being different from each other.
[0100] For example, for a duration Tc equal to the value t1, if the temperature of the cooling fluid is equal to T1, the value of the variable REP is equal to N1, if the temperature of the cooling fluid is equal to T2, the value of the variable REP is equal to N2, and if the temperature of the cooling fluid is equal to T3, the value of the variable REP is equal to N3, the values N1, N2, N3 being different from each other.
[0101] The curves C1, C2, C3 are determined, for example, based on numerical simulations and tests involving multiple steps for keeping the motor vehicle 1 stationary on a slope.
[0102] Referring again to Figure 2 .
[0103] During step 38, the value of the variable VAR is compared with the value of the variable REP.
[0104] If the value of the variable VAR is lower than the value of the variable REP (step 40), then during step 41, the value of the variable VAR is incremented, and the method continues with step 23.
[0105] If the value of the variable VAR is higher than the value of the variable REP (step 40), then during step 42, the command device 6 transmits a second signal to the device for commanding the parking brakes (not depicted) of the motor vehicle 1 to enable the parking brakes of the motor vehicle 1.
[0106] In addition, a man-machine interface (not depicted) of the motor vehicle 1 alerts the driver of the motor vehicle 1 that the parking brake is engaged.
[0107] The man-machine interface includes, for example, an indicator light.
[0108] The variable REP determined in step 39 represents the maximum number of repetitions of steps 23 to 41 in order to prevent the motor 2 from overheating.
[0109] The command device 6 allows the temperature of the motor 2 to be controlled in such a way as to avoid overheating of the motor 2 when the motor vehicle 1 is stationary on a slope, without adding a temperature probe to the motor 2.
[0110] As a variant, the value of the torque applied to the rotor shaft 3 can be determined by means other than the torque estimation device, for example using a model of the motor 2.
[0111] As a variant, the value of the speed of the motor vehicle 1 can be determined by means other than the speed sensor 8, for example based on information transmitted along the bus of the motor vehicle 1.
[0112] As a variant, the value of the temperature of the cooling fluid can be determined by means other than the temperature sensor 9, for example using a model of the motor 2.
[0113] As a variant, the value of the set torque can be determined by means other than the accelerator pedal 10, for example based on information transmitted along the bus of the motor vehicle 1.
Claims
1. A method for controlling an electric machine (2) for propelling an electric or hybrid motor vehicle (1), characterized in that, The method includes: - a) detecting that the motor vehicle (1) has come to a standstill on a slope, - b) determining a reference duration based on the temperature of the cooling fluid of the electric motor (2) and the torque applied to the rotor shaft (3) of the electric motor when the motor vehicle is at a standstill on the slope, - c) starting a timer (13) when it is detected that the motor vehicle has come to a standstill on the slope, - d) determining a commanded torque for commanding the electric motor based on a set torque and based on a comparison between the reference duration and the time elapsed since the timer was started when the motor vehicle is at a standstill on the slope, and - e) commanding the electric motor (2) based on the commanded torque.
2. The method according to claim 1, wherein When the motor vehicle is not at a standstill on the slope or the time elapsed since the timer was started is less than the reference duration, the commanded torque for commanding the electric motor (2) is equal to the set torque.
3. The method according to one of claims 1 and 2, wherein, Detecting that the motor vehicle (1) has come to a standstill on the slope includes comparing the torque applied to the rotor shaft (3) of the electric motor (2) with a first predetermined threshold and comparing the speed of the motor vehicle (1) with a second predetermined threshold, and when the torque is higher than the first predetermined threshold and the speed is lower than the second predetermined threshold, the motor vehicle is at a standstill on the slope.
4. The method according to any one of claims 1 to 3, wherein, Step a) further includes initializing a variable representing the number of repetitions of steps b) to d), the variable being set to a predetermined initial value, and wherein when the time elapsed since the timer was started is greater than or equal to the reference duration, determining the commanded torque for commanding the electric motor (2) includes: - comparing the commanded torque with a predetermined detection torque, - determining a first intermediate torque, which is equal to the predetermined detection torque when the commanded torque is lower than the predetermined detection torque, or which is equal to the commanded torque minus a first correction torque when the commanded torque is higher than the predetermined detection torque, - updating the commanded torque for the first time such that the commanded torque is equal to the first intermediate torque, - when commanding the electric motor (2) based on the commanded torque equal to the first intermediate torque, comparing the speed of the motor vehicle with the second predetermined threshold, and if the speed of the motor vehicle (1) is higher than the second predetermined threshold, the method further includes: - if the speed of the motor vehicle is higher than the second predetermined threshold, determining a second intermediate torque, which is equal to the commanded torque plus a second correction torque, - updating the commanded torque for the second time such that the commanded torque is equal to the second intermediate torque, - if the variable is equal to the initial value, determining the number of repetitions of steps b) to e) based on the temperature of the cooling fluid and the time elapsed since the timer was started, - comparing the value of the variable with the number of repetitions, and - if the value of the variable is lower than the number of repetitions, incrementing the value of the variable and repeating steps b) to e).
5. The method according to claim 4, wherein If the value of the variable is higher than the number of repetitions, the method further includes activating the parking brake of the motor vehicle (1).
6. The method according to one of claims 4 and 5, wherein, If the speed of the motor vehicle (1) is lower than the second predetermined threshold and the torque applied to the rotor shaft of the electric machine (2) is higher than the first predetermined threshold, the commanded torque remains unchanged.
7. A control device (6) for controlling an electric machine (2) for propelling an electric or hybrid motor vehicle (1), characterized in that, The device comprises: - a detection device (11) configured to detect that the motor vehicle (1) has come to a standstill on a slope, - a first determination device (12) configured to determine a reference duration based on the temperature of the cooling fluid of the electric machine (2) and the torque applied to the rotor shaft (3) of the electric machine (2) when the motor vehicle is at a standstill on the slope, - a timer (13), the detection device (11) being further configured to start the timer when it detects that the motor vehicle has come to a standstill on the slope, - a second determination device (14) configured to determine a commanded torque for commanding the electric machine (2) based on a set torque and based on a comparison between the reference duration and the time elapsed since the timer (13) was started when the motor vehicle is at a standstill on the slope, and - a command device (15) configured to command the electric machine (2) based on the commanded torque.
8. The control device according to claim 7, wherein, The first determination device (11) comprises a predetermined table (TAB) that associates at least the reference duration with values of the temperature of the cooling fluid and values of the torque applied to the rotor shaft of the electric machine.
9. An electric or hybrid motor vehicle (1) comprising a propulsion electric machine (2) and a control device (6) as claimed in one of claims 7 and 8.