Motor control method and motor control device

Abstract

In the present invention, a gradient parameter that indicates a road surface gradient for an electric vehicle is acquired, a temperature parameter that indicates the temperature in a motor control system including an electric motor is acquired, and torque control processing is executed in which when at least one of the gradient parameter and the temperature parameter is greater than or equal to a prescribed threshold value that has been respectively defined therefor, the upper limit of demand torque is set to a corrected torque upper limit that is less than a prescribed basic torque upper limit. In the torque control processing, a first torque is determined from the gradient parameter, a second torque for imparting a prescribed acceleration to the electric vehicle is determined, and the corrected torque upper limit is determined by referring to the first torque and the second torque and correcting the basic torque upper limit.

Description

[Technical Field]

[0001] The present invention relates to a motor control method and a motor control device that include an electric motor as a drive source. [Background technology]

[0002] JP4946100B describes a motor control method comprising: a first torque limiting means that limits the torque according to the motor temperature when the motor temperature exceeds a first predetermined value in order to prevent the motor from failing; and a second torque limiting means that, in order to prevent the motor temperature from reaching the first predetermined value under high load conditions such as when an electric vehicle is traveling up a long incline, limits the torque to a certain upper limit that is less restrictive than that of the first torque limiting means when the motor temperature exceeds a second predetermined value which is smaller than the first predetermined value. [Overview of the project]

[0003] In the control method described in JP4946100B, when a vehicle is traveling on an uphill road with a gradient above a certain level, even if the motor has sufficient maximum torque performance and the motor temperature is within the allowable range, the second torque limiting means (a limit to suppress temperature rise) functions and limits the upper limit of the motor torque, which may prevent the desired driving performance from being achieved when traveling on an uphill road.

[0004] Therefore, the present invention aims to achieve both the suppression of excessive temperature rise within the motor control system and the assurance of vehicle driving performance when driving on an uphill road.

[0005] According to one aspect of the present invention, a motor control method is provided for controlling the operation of an electric motor in an electric vehicle equipped with an electric motor as a drive source, based on a predetermined required torque. In this motor control method, a gradient parameter indicating the road surface gradient of the electric vehicle is obtained, and a temperature parameter indicating the temperature within the motor control system including the electric motor is obtained. If at least one of the gradient parameter and the temperature parameter is greater than or equal to a predetermined threshold defined for each, a torque limiting process is performed to set the upper limit of the required torque to a corrected torque upper limit that is smaller than a predetermined basic torque upper limit. In the torque limiting process, a first torque is determined from the gradient parameter, a second torque is determined to give the electric vehicle a predetermined acceleration, and a corrected torque upper limit is determined by correcting the basic torque upper limit by referring to the first torque and the second torque. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a block diagram showing the main configuration of the vehicle drive system according to the first embodiment. [Figure 2] Figure 2 is a block diagram illustrating the configuration of the motor controller according to the first embodiment. [Figure 3] Figure 3 illustrates an example of a basic torque limiter. [Figure 4] Figure 4 is a block diagram illustrating the configuration of the gradient torque estimation unit. [Figure 5] Figure 5 is an explanatory diagram showing the dynamic model of an electric vehicle. [Figure 6] Figure 6 is a flowchart showing the processing of the upper limit torque limit request determination unit. [Figure 7] Figure 7 is a block diagram illustrating the configuration of the torque limiting unit. [Figure 8] Figure 8 is a flowchart showing the overall processing of the motor control method according to the first embodiment. [Figure 9] Figure 9 is a block diagram showing the main configuration of the vehicle drive system according to the second embodiment. [Figure 10]Figure 10 is a block diagram illustrating the configuration of the motor controller. [Figure 11] Figure 11 illustrates the method for estimating gradient torque. [Figure 12] Figure 12 is a block diagram illustrating the configuration of the gradient torque estimation unit. [Figure 13] Figure 13 shows an example of a map that determines acceleration torque. [Figure 14] Figure 14 is a block diagram illustrating the configuration of the torque limiting unit. [Figure 15] Figure 15 is a flowchart showing the overall processing of the motor control method according to the second embodiment. [Figure 16] Figure 16 is a graph showing the control results for the comparative example and the example. [Modes for carrying out the invention]

[0007] The embodiments of the present invention will be described below with reference to the drawings.

[0008] [First Embodiment] Figure 1 is a block diagram showing the main components of a vehicle drive system 100 installed in an electric vehicle. As shown in the figure, the vehicle drive system 100 mainly comprises a battery 1, a vehicle controller 2, a motor controller 3 as a motor control device, a PWM (Pulse Width Modulation) inverter 4, an electric motor 5, a reduction gear 6, a drive shaft 8, drive wheels 9a, 9b, a rotation sensor 20, a current sensor 21, a voltage sensor 22, and a thermistor 23. An electric vehicle is a vehicle that uses an electric motor as its drive source. Any vehicle that can use the electric motor 5 as part or all of its drive source is an electric vehicle. In other words, electric vehicles include not only electric vehicles but also hybrid vehicles and fuel cell vehicles.

[0009] Battery 1 is connected to the electric motor 5 via a PWM inverter 4 and supplies driving power to the electric motor 5 by discharging. Battery 1 is also configured to be rechargeable by receiving regenerative power from the electric motor 5.

[0010] The vehicle controller 2 is comprised of a computer consisting of, for example, a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and an input / output interface (I / O interface). Based on the driver's operation of the accelerator pedal or brake pedal and other vehicle conditions, the vehicle controller 2 determines the torque required for the electric vehicle (hereinafter referred to as "higher-level required torque T"). * It generates a signal (referred to as "...") and outputs it to the motor controller 3.

[0011] The motor controller 3 is comprised of a computer consisting of, for example, a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and an input / output interface (I / O interface). The motor controller 3 receives a higher-level requested torque T from the vehicle controller 2. * Based on the input signals from various sensors, the following processes are executed to control the PWM inverter 4 (three-phase duty cycle command value D u ,D v ,D w It is programmed to generate ).

[0012] The PWM inverter 4 includes, for example, two switching elements (such as IGBTs (Insulated Gate Bipolar Transistors) or MOS-FETs (metal-oxide-semiconductor field-effect transistors) power semiconductor elements) corresponding to each phase. The PWM inverter 4 receives the three-phase duty cycle command value D from the motor controller 3. u ,D v ,D wA drive signal for the switching element is generated based on the comparison result with a carrier triangular wave of a predetermined frequency. Then, the PWM inverter 4 turns on / off the switching element according to the drive signal, converts the direct current supplied from the battery 1 into an alternating current, and adjusts the current supplied to the electric motor 5. Further, the PWM inverter 4 inversely converts the alternating current generated by the electric motor 5 due to the regenerative braking force into a direct current, and adjusts the current supplied to the battery 1.

[0013] The electric motor 5 is constituted by, for example, a three-phase alternating current motor, and generates a driving force by the alternating current supplied from the PWM inverter 4. The driving force generated by the electric motor 5 is transmitted to a pair of left and right drive wheels 9a and 9b via the reduction gear 6 and the drive shaft 8. Further, when the electric motor 5 is rotated being carried along by the drive wheels 9a and 9b, the electric motor 5 generates a regenerative braking force, and recovers the kinetic energy of the vehicle drive system 100 as electric energy.

[0014] The reduction gear 6 is constituted by, for example, a plurality of gears. The reduction gear 6 generates a driving torque or a braking torque proportional to the reduction ratio by reducing the rotational speed of the electric motor 5 and transmitting it to the drive shaft 8.

[0015] The rotation sensor 20 detects the rotor position θ of the electric motor 5 and outputs it to the motor controller 3. The rotation sensor 20 is constituted by, for example, a resolver or an encoder. The current sensor 21 detects the current flowing through the electric motor 5 and outputs it to the motor controller 3. In the present embodiment, the current sensor 21 detects the three-phase alternating currents i u , i v , i w of the electric motor 5 respectively. Note that, using the current sensor 21, any two-phase currents may be detected, and the remaining one-phase current may be obtained by calculation. The voltage sensor 22 detects the DC voltage value V dc of the battery 1 and outputs it to the motor controller 3. The thermistor 23 detects the temperature of the stator winding of the electric motor 5 (hereinafter, also simply referred to as "winding temperature T emp ") and outputs it to the motor controller 3.

[0016] Figure 2 is a block diagram illustrating the configuration of the motor controller 3. As shown in the figure, the motor controller 3 is programmed to function as a basic torque limiter 31, a rotational speed calculation unit 32, a gradient torque estimation unit 33, an upper limit torque limit request determination unit 34, a torque limiting unit 35, a vibration damping control unit 36, and a torque control unit 37.

[0017] The basic torque limiter 31 receives the higher-level torque T from the vehicle controller 2. * , DC voltage value V from voltage sensor 22 dc , and the rotational speed RPM of the electric motor 5 are used as input, with the maximum torque T as the basic torque upper limit. max Then, the basic required torque T1 is calculated.

[0018] Figure 3 illustrates the processing performed by the basic torque limiter 31. As shown in the figure, the basic torque limiter 31 first processes the rotational speed RPM and the DC voltage value V dc Therefore, the maximum torque T corresponds to the positive output limit torque of the electric motor 5. max and the minimum torque T corresponding to the negative power limit torque. min The basic torque limiter 31 sets the higher required torque T. * Maximum torque T max and minimum torque T min The value obtained by limiting is defined as the basic required torque T1. Furthermore, the basic torque limiter 31 is determined by the maximum torque T max The system also outputs the basic required torque T1 to the torque limiting unit 35.

[0019] The rotational speed calculation unit 32 takes the rotor position θ as input and calculates the mechanical angular velocity ω, which suggests the rotational speed of the electric motor 5, from the amount of change in the rotor position θ over time. m [rad / s], electrical angular velocity ω e The rotational speed calculation unit 32 calculates the rotational speed in rad / s and the rotational speed in RPM [rpm]. Then, the rotational speed calculation unit 32 calculates the mechanical angular velocity ω m The gradient torque estimation unit 33 and the vibration control unit 36 ​​receive the electrical angular velocity ω eThe torque control unit 37 outputs the torque value, and the rotational speed RPM outputs the upper limit torque limit request determination unit 34.

[0020] The gradient torque estimation unit 33 calculates the mechanical angular velocity ω from the rotational speed calculation unit 32. m And, taking the limited request torque T2 from the torque limiting unit 35 (described later) as input, the gradient torque T is used as the first torque. s The gradient torque T of this embodiment is calculated. s This is defined as the torque required to maintain the vehicle speed below a certain value (especially 0) when an electric vehicle is traveling uphill. In other words, gradient torque T s This is defined as the torque that counteracts the rollback force acting on the electric vehicle due to the gradient of the uphill road.

[0021] Figure 4 is a block diagram illustrating the configuration of the gradient torque estimation unit 33. As shown in the figure, the gradient torque estimation unit 33 first calculates the transfer function G p The filter H1(s) / G is determined as the quotient of (s) with respect to the filter H1(s). p (s) The mechanical angular velocity ω m By filtering the results, the estimated torque T est The following is calculated. Note that the transfer function G p (s) is the mechanical angular velocity ω m From the output torque of the electric motor 5 (hereinafter simply referred to as "motor torque T") m This represents the transfer characteristics to the filter H1(s), which is also called the "transfer function G". p It is constructed as a low-pass filter with an order greater than or equal to the difference between the numerator and denominator orders of (s).

[0022] Furthermore, the gradient torque estimation unit 33 processes the limited-request torque T2 with the filter H1(s) described above, thereby obtaining the reference torque T ref The gradient torque estimation unit 33 calculates the reference torque T. ref Estimated torque T est Subtract the deviation T from those values. err The gradient torque estimation unit 33 calculates the deviation T. err Filter Hz By processing with (s), the disturbance torque T as a gradient parameter is obtained. d The gradient torque estimation unit 33 calculates the disturbance torque T. d By processing it with filter H2(s), the gradient torque T s We seek.

[0023] In the following, the transfer function G p (s), and each filter H1(s), H z (s), H2(s) will be explained in detail.

[0024] Figure 5 shows an example of a mechanical model of an electric vehicle. The following equations of motion 1-5 can be derived from the illustrated mechanical model.

[0025]

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[0026] Note that each letter in equations 1 to 5 includes those already explained and is defined as follows.

[0027] J m : Electric motor inertia J w Inertia of the drive wheels M: Vehicle mass K D Torsional rigidity of the wheel drive system K t : Coefficient related to the friction between the tire and the road surface N: Overall gear ratio r: Tire load radius ω m : Mechanical angular velocity of an electric motor T m : Motor Torque T D Torque of the drive wheels F: Force applied to the vehicle V: Vehicle speed ω w Angular velocity of the drive wheels

[0028] Referring to the above equations of motion 1-5, the transfer function G p (s) can be expressed by the following equation 6. Furthermore, the coefficients a1 to a4 and b0 to b3 in equation 6 are expressed by the following equations 7 to 14.

number

[0029] The transfer function G shown in the above formula more p When we examine the poles and zeros of (s), we find that one pole and one zero are extremely close in value. This means that α and β in equation 15 below are extremely close in value.

[0030]

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[0031] Therefore, by performing pole-zero cancellation, approximating α=β in Equation 15, we obtain the (quadratic) / (cubic) form transfer function G as shown in Equation 16 below. p (s) can be obtained.

[0032]

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[0033] Next, we will explain the filter H1(s). The filter H1(s) is H1(s) / G p From the perspective of using (s) as the proprietary transfer function, it is constructed by a first-order low-pass filter defined by the following equation 17.

[0034]

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[0035] The time constant τ1 is set to an appropriate value, for example, on the order of tens of ms, depending on the torque response characteristics of the electric motor 5.

[0036] Next, filter H zLet's explain (s). First, by rewriting equation 16 above, we obtain the following equation 18.

[0037]

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[0038] However, each coefficient in Equation 18 is determined by Equations 19 to 23.

[0039]

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[0040] Based on the above, filter H z (s) is determined by the following equation 24.

[0041]

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[0042] However, "ζ c " is "ζ z It is defined as a constant smaller than "[ ]".

[0043] Next, we will explain the filter H2(s). The filter H2(s) is a disturbance torque T d It is configured as a low-pass filter that removes high-frequency components other than the effects of the gradient (effects of fine undulations, cracks, and steps on the road surface). Specifically, filter H2(s) is composed of a first-order low-pass filter defined by the following equation 25.

[0044]

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[0045] The time constant τ2 is set to an appropriate value, for example, on the order of several hundred ms, depending on the expected road surface conditions.

[0046] Next, returning to Figure 2, the upper limit torque limit request determination unit 34 will be explained. The upper limit torque limit request determination unit 34 determines the gradient torque T s , winding temperature T emp The rotational speed (RPM) and the basic required torque T1 are inputs, and the limit execution flag f lim To define.

[0047] Figure 6 is a flowchart showing the processing of the upper limit torque limit request determination unit 34. As shown in the figure, in steps S110 to S140, the upper limit torque limit request determination unit 34 determines the gradient torque T s The gradient torque threshold T s_th Whether or not the winding temperature T emp The temperature threshold T emp_th Whether or not the vehicle speed V is above the low vehicle speed threshold V _lo From high vehicle speed threshold V _hi Whether or not it falls within the range, and whether the basic required torque T1 is within the required torque threshold T 1_th The system then determines whether the above is true or not. If all the results of each determination are positive, the upper limit torque limit request determination unit 34 sets the limit execution flag f lim Set to "1", and if either is negative, the restricted execution flag f lim Set it to "0".

[0048] The vehicle speed V used for the determination is calculated from the rotational speed (RPM) based on the following equation 26.

[0049]

number

[0050] Here, the gradient torque threshold T used in S110 s_th The appropriate gradient torque T1 is used as a criterion for determining whether the gradient is large enough to require the implementation of a limit on the upper limit of the basic required torque T1 (hereinafter also simply referred to as "torque limit") (i.e., whether it is a steep uphill road). s The value is determined to be [value]. Also, the temperature threshold T used in S120 emp_th The winding temperature T empis set to a value of the winding temperature T that is appropriate as a criterion for determining whether or not the torque limit has been reached to a degree that requires execution of the torque limit. emp is set to the value.

[0051] Also, the low vehicle speed threshold V used in S130 _lo and the high vehicle speed threshold V _hi are set to values of the vehicle body speed V that are appropriate as criteria for determining whether or not the vehicle speed of the electric vehicle during forward travel is within a predetermined vehicle speed range that requires execution of the torque limit.

[0052] Here, in a region where the vehicle body speed V is below a certain level (low vehicle speed region), it is assumed that the travel time on an uphill road will be prolonged because the electric vehicle cannot reach the desired vehicle speed by executing the torque limit or because it takes an excessive amount of time to reach the desired vehicle speed. In this case, the electric motor 5 will continue to output torque for a long time in the low vehicle speed region (low rotational speed region of the electric motor 5). Therefore, in the above low vehicle speed region, it is assumed that execution of the torque limit will rather promote an increase in the winding temperature T emp Considering this point, in the present embodiment, the low vehicle speed threshold V _lo is set to a value of the vehicle body speed V that is suitable from the viewpoint of determining the low vehicle speed region in which execution of the torque limit should be prohibited. That is, the low vehicle speed threshold V _lo is set to an appropriate value from the viewpoint of determining the low vehicle speed region in which execution of the torque limit can promote an excessive temperature rise within the motor control system.

[0053] On the other hand, in a vehicle speed range where the vehicle body speed V is above a certain level (high vehicle speed region), it is assumed that the gradient on the uphill road is relatively small and an excessive increase in the winding temperature T emp is unlikely to occur. Therefore, if the torque limit is executed in such a scene, it is assumed that the acceleration performance of the electric vehicle will be uselessly impaired even though the possibility of an excessive temperature rise within the motor control system is low. Considering this point, in the present embodiment, the high vehicle speed threshold V _hi is set to a value of the vehicle body speed V that is suitable from the viewpoint of determining the high vehicle speed region in which execution of the torque limit should be prohibited. That is, the high vehicle speed threshold V _hiIt is determined to be an appropriate value from the viewpoint of determining a high vehicle speed range that may uselessly impair the acceleration performance of the electric vehicle by executing torque limitation.

[0054] And in the vehicle speed range (medium vehicle speed range) excluding the above low vehicle speed range and high vehicle speed range, it is assumed that the gradient is relatively large and a scene where an excessive rise in the winding temperature T emp may occur. Therefore, in the present embodiment, execution of torque limitation is allowed in such a scene.

[0055] Furthermore, the required torque threshold T 1_th used in S140 is determined as a reference value for determining whether there is an acceleration request (acceleration intention by the driver) for the electric vehicle.

[0056] Here, when the basic required torque T1 is below a certain level (when it is estimated that there is no acceleration intention), a scene where the driver is not performing an accelerator pedal operation, or immediately after an on-operation or off-operation of the accelerator pedal is assumed. In a scene where the accelerator pedal operation is not performed, in the first place, it is difficult for the motor torque T m to reach a level that causes an increase in the winding temperature T emp , so torque limitation is unnecessary. Also, immediately after an on-operation or off-operation of the accelerator pedal, an error is likely to occur in the calculation of the gradient torque T s due to the pitching of the electric vehicle. For this reason, in such a scene, there is a concern about a decrease in the accuracy of the corrected torque upper limit (the corrected torque upper limit T s lim lim ) calculated based on the gradient torque T s . Considering this point, in the present embodiment, the required torque threshold T 1_th is determined to be an appropriate value of the basic required torque T1 from the viewpoint of determining a situation without an acceleration intention where torque limitation should be prohibited.

[0057] And the upper limit torque limitation request determination unit 34 outputs the set limitation execution flag f lim to the torque limitation unit 35.

[0058] Next, the torque limiting section 35 will be described.

[0059] Figure 7 is a block diagram illustrating the configuration of the torque limiting unit 35. As shown in the figure, the torque limiting unit 35 has a limiting execution flag f lim If the value is "0" (meaning there is no request for an upper limit torque), the basic requested torque T1 is output as the limited requested torque T2. On the other hand, the torque limiting unit 35 controls the limiting execution flag f lim If it is "1" (if there is a request for an upper limit torque), the basic required torque T1 and the corrected torque upper limit T lim The value obtained by the minimum select is output as the limited required torque T2.

[0060] Furthermore, the torque limiting unit 35 has a corrected torque upper limit T lim The gradient torque T s and acceleration torque T acc The sum of and the maximum torque T max The calculation is performed using the minimum select. Note that acceleration torque T acc This refers to the motor torque T, which is determined from the perspective of obtaining the minimum acceleration required for an electric vehicle to not obstruct the flow of traffic when traveling uphill. m It is set to the value of . In particular, the acceleration torque T of this embodiment acc This is a fixed value determined experimentally in advance and stored in a predetermined memory area accessible by the motor controller 3.

[0061] According to the control logic of the motor control method of this embodiment described above, when an electric vehicle is traveling uphill, the temperature parameter (winding temperature T emp ) and gradient parameter (disturbance torque T d Depending on the circumstances, an appropriate limit will be imposed on the upper limit of the basic required torque T1.

[0062] Returning to Figure 2, the vibration damping control unit 36 ​​determines the final required torque T3 by performing a known process (such as the process described in Japanese Patent No. 3508742) to suppress torsional vibration of the drive shaft 8 in relation to the limited required torque T2, and outputs it to the torque control unit 37.

[0063] Furthermore, the torque control unit 37, based on the final required torque T3 and other necessary input values, controls the three-phase duty cycle command value D according to known motor control logic (current vector control and voltage phase control, etc.). u ,D v ,D w To define.

[0064] Figure 8 shows a flowchart illustrating the overall process in the motor control method of this embodiment described above.

[0065] The configuration of the motor control method of this embodiment described above, and its effects, will now be explained.

[0066] In this embodiment, a motor control method is provided for controlling the operation of an electric motor 5 in an electric vehicle equipped with an electric motor 5 as a drive source, based on a predetermined required torque.

[0067] This motor control method uses a gradient parameter (disturbance torque T) that indicates the road surface gradient of the electric vehicle. d ) is obtained, and a temperature parameter (winding temperature T) that suggests the temperature within the motor control system including the electric motor 5 is obtained. emp ) is obtained, and at least one of the gradient parameter and temperature parameter is set to a predetermined threshold (gradient torque threshold T) defined for each. s_th or temperature threshold T emp_th If it is greater than or equal to ), the upper limit of the required torque is set to a predetermined basic torque upper limit (maximum torque T max Correction torque upper limit T is smaller than ) lim The torque limiting process (upper limit torque limit request determination unit 34 and torque limiting unit 35) is executed to set the torque limit.

[0068] In particular, in torque limiting processing, the gradient parameter (disturbance torque T) d ) from the first torque (gradient torque T s ) is determined, and a second torque (acceleration torque T) is set to give the electric vehicle a predetermined acceleration. acc ) is determined, and the first torque (gradient torque T s) and second torque (acceleration torque T acc Refer to the basic torque limit (maximum torque T) max By correcting the above, the correction torque upper limit T lim To define.

[0069] This allows for appropriate limitation of the upper limit of the basic required torque T1 in scenarios where an electric vehicle is traveling uphill, depending on the temperature level within the motor control system and / or the magnitude of the gradient. Therefore, it becomes possible to suppress excessive temperature rise in the motor control system and ensure the driving performance (acceleration performance) of the electric vehicle when traveling uphill.

[0070] In particular, in this embodiment, the gradient torque T s This is set to a torque that counteracts the rollback force acting when driving uphill. And the acceleration torque T acc This is determined to be the torque required to obtain acceleration that does not disrupt the flow of traffic. And the correction torque upper limit T lim Since this is determined as a composite value of these factors, it becomes possible to more reliably achieve both the suppression of temperature rise and the assurance of driving performance when driving on uphill roads.

[0071] Furthermore, in this embodiment, the gradient torque T s The output torque (motor torque T) of the electric motor 5. m The estimated torque T is an estimated value of ). est And the rotational speed of electric motor 5 (mechanical angular velocity ω m Disturbance torque T is an estimated value of the disturbance determined according to ). d The calculation is performed from this (gradient torque estimation unit 33).

[0072] This results in a gradient torque T s A more specific control logic is realized for calculating the gradient torque T. In particular, the gradient torque T can be calculated based on signals that can be obtained within the vehicle drive system 100, without using a separate sensor to detect the magnitude of the gradient. s It can perform calculations.

[0073] Furthermore, in this embodiment, the vehicle speed parameter (vehicle speed V) that indicates the vehicle speed of the electric vehicle is within a predetermined vehicle speed range (V _lo ≦V≦V _hi When it deviates from ), gradient torque T s Or winding temperature T emp and each predetermined threshold T s_th ,T emp_th Regardless of the relative magnitudes, the upper limit of the required torque is set to the maximum torque T. max Set to (No. S130 and S160).

[0074] This allows for the proper detection of low-speed ranges where torque limiting could actually exacerbate excessive temperature increases within the motor control system, and high-speed ranges where excessive temperature increases are unlikely to occur and torque limiting is unnecessary. Torque limiting can then be prohibited in these scenarios. Therefore, torque limiting can be restricted to medium-speed ranges where excessive temperature increases within the motor control system are a concern, such as when driving on relatively steep uphill roads. As a result, a better balance can be achieved between suppressing excessive temperature increases during uphill driving and ensuring the driving performance of electric vehicles.

[0075] Furthermore, instead of the configuration that prohibits the execution of torque limiting in the low-speed and high-speed ranges described above, the execution of torque limiting itself is permitted, but the limit value when said torque limiting is executed (i.e., corrected torque upper limit T) lim A configuration that adjusts ) as appropriate may also be adopted.

[0076] In particular, the vehicle speed V is within the above vehicle speed range (V _lo ≦V≦V _hi When it deviates from ), acceleration torque T acc Adjust the correction torque upper limit T lim A control logic that increases this further may be adopted. In this case, the correction torque upper limit T can be adjusted according to the magnitude of the vehicle speed V. lim A configuration that changes the size in stages or continuously may also be adopted.

[0077] Furthermore, in this embodiment, the basic required torque T1, which is determined according to the required driving force for the electric vehicle, is set to a predetermined torque threshold (required torque threshold T 1_th If less than ), the gradient torque T s Or winding temperature T emp and their respective thresholds T s_th ,T emp_th Regardless of the relative magnitudes, the upper limit of the required torque is set to the maximum torque T. max Set to (No. S140 and S160).

[0078] This allows the system to appropriately identify scenarios where there is no benefit to torque limiting during uphill driving, i.e., scenarios where excessive temperature rise within the motor control system is unlikely to occur, by referring to the basic required torque T1. In such scenarios, torque limiting can be appropriately prohibited. Therefore, torque limiting can be limited to torque ranges where excessive temperature rise within the motor control system is a concern. As a result, a better balance can be achieved between suppressing excessive temperature rise during uphill driving and ensuring the driving performance of electric vehicles.

[0079] Furthermore, the above-mentioned basic required torque T1 is the required torque threshold T 1_th Instead of a configuration that prohibits the execution of the upper torque limit when it is less than a certain value, the execution of the torque limit itself is permitted, but the corrected torque upper limit T when the torque limit is executed is instead used. lim A configuration that allows for appropriate adjustment of size may also be adopted.

[0080] In particular, the basic required torque T1, which is determined according to the required driving force for electric vehicles, is the required torque threshold T 1_th If it is less than, acceleration torque T acc Adjust the correction torque upper limit T lim A control logic that increases this further may be adopted. In this case, the correction torque upper limit T can be set according to the magnitude of the basic required torque T1. lim A configuration that changes the size in stages or continuously may also be adopted.

[0081] Furthermore, in this embodiment, a motor controller 3 is provided that functions as a motor control device suitable for implementing a motor control method.

[0082] This motor controller 3 uses a gradient parameter (disturbance torque T) that indicates the road surface gradient of the electric vehicle. d A gradient parameter acquisition unit (gradient torque estimation unit 33) acquires the following: a temperature parameter (winding temperature T) that indicates the temperature within the motor control system including the electric motor 5. emp A temperature parameter acquisition unit (upper limit torque limit request determination unit 34) acquires the gradient parameter and a temperature parameter, and at least one of the gradient parameter and the temperature parameter is determined to be a predetermined threshold (gradient torque threshold T) s_th or temperature threshold T emp_th If it is greater than or equal to ), the upper limit of the required torque is set to a predetermined basic torque upper limit (maximum torque T max Correction torque upper limit T is smaller than ) lim It includes a torque limiting unit 35 that performs torque limiting processing to set a torque limit.

[0083] In particular, the torque limiting unit 35 controls the gradient parameter (disturbance torque T). d ) from the first torque (gradient torque T s ) is determined, and a second torque (acceleration torque T) is set to give the electric vehicle a predetermined acceleration. acc ) is determined, and the first torque (gradient torque T s ) and second torque (acceleration torque T acc Refer to the basic torque limit (maximum torque T) max By correcting the above, the correction torque upper limit T lim To define.

[0084] [Second Embodiment] The second embodiment will be described below. Elements similar to those in the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0085] Figure 9 is a block diagram showing the main configuration of a vehicle drive system 200 mounted on an electric vehicle. As shown in the figure, the vehicle drive system 200 of this embodiment differs from the first embodiment in that, in addition to the various input values ​​described above, the motor controller 3 takes as input the vehicle speed V of the electric vehicle detected by a vehicle speed sensor (not shown) and the longitudinal acceleration a1 detected by a longitudinal acceleration sensor (not shown) and performs various calculations.

[0086] Figure 10 is a block diagram illustrating the configuration of the motor controller 3 of this embodiment. In the motor controller 3 of this embodiment, the gradient torque estimation unit 33 calculates the mechanical angular velocity ω m And instead of the limited required torque T2, the vehicle speed V and longitudinal acceleration a1 are used as inputs to calculate the gradient torque T s Perform the calculation.

[0087] Figure 11 shows the gradient torque T. s This figure illustrates the estimation method. Generally, the relationship between the driving force F acting on the tires of an electric vehicle, the vehicle weight M, the acceleration due to gravity g, and the gradient angle α of the road surface is as shown in Figure 11. Therefore, the driving force F is the sum of the component of the acceleration due to gravity in the direction of the slope and the net acceleration (hereinafter also simply referred to as "vehicle acceleration a") which is the acceleration of the vehicle body excluding the effect of the gradient. Thus, the relationship in Equation 27 below holds.

[0088]

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[0089] On the other hand, the longitudinal acceleration a1 detected by the longitudinal acceleration sensor includes the effect of gravitational acceleration corresponding to the gradient angle α in addition to the vehicle acceleration a mentioned above. Therefore, the driving force F can be expressed as the product of the vehicle weight M and the longitudinal acceleration a1. Accordingly, substituting "M × a1" for "F" in equation 27 and dividing both sides by "M" yields the following equation 28.

[0090]

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[0091] Furthermore, rearranging equation 28 yields equation 29.

[0092]

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[0093] The vehicle acceleration a is calculated by differentiating the vehicle velocity V, as shown in equation 30 below.

[0094]

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[0095] Furthermore, a torque (i.e., gradient torque T) that counteracts the rollback force acting on the electric vehicle due to the gradient. s ) can be expressed by the following equation 31.

[0096]

number

[0097] Therefore, substituting equation 29 into equation 31 yields equation 32.

[0098]

number

[0099] Figure 12 is a block diagram illustrating the configuration of the gradient torque estimation unit 33. As shown in the figure, the gradient torque estimation unit 33 includes an acceleration calculation unit 331, a subtraction unit 332, and a gain unit 333.

[0100] The acceleration calculation unit 331 calculates the vehicle acceleration a from the rate of change of the vehicle speed V per unit time according to equation 30 and outputs it to the subtraction unit 332. The subtraction unit 332 subtracts the longitudinal acceleration a1 from the vehicle acceleration a according to equation 29 to obtain the gradient acceleration a which corresponds to the effect of gravitational acceleration according to the gradient. sThe function (=gsinα) is calculated and output to the gain unit 333. The gain unit 333 calculates the gradient acceleration a according to equation 31. s The gradient acceleration a is calculated by multiplying the vehicle weight M, the overall gear ratio N, and the gain Mr / N determined from the load radius r of the drive wheels 9a and 9b. s Convert this to a torque equivalent value, and this becomes the gradient torque T s Output as follows.

[0101] Returning to Figure 11, the upper limit torque limit request determination unit 34 of this embodiment determines the gradient torque T s and winding temperature T emp Using the input as acceleration torque T acc To define.

[0102] Figure 13 shows the acceleration torque T. acc This figure shows an example of a map that defines acceleration torque T. acc However, winding temperature T emp The lower the gradient torque T, the lower the gradient torque T. s The map is set to increase as the value decreases. This map is pre-stored in a predetermined memory area accessible by the motor controller 3. Furthermore, the map may be configured in a format preferred from a computational processing standpoint, such as a linear interpolation type lookup table or a function with conditional judgments.

[0103] The upper limit torque limit request determination unit 34 refers to the above map to determine the winding temperature T emp and gradient torque T s Appropriate acceleration torque T pre-scheduled accordingly acc It is possible to determine this.

[0104] Furthermore, Figure 14 shows a block diagram illustrating the configuration of the torque limiting unit 35 in this embodiment. As shown in the figure, the torque limiting unit 35 controls the fixed acceleration torque T described in the first embodiment. acc Instead, the variable acceleration torque T calculated by the upper limit torque limit request determination unit 34 acc The following operations are performed similarly, taking the input as the input.

[0105] Figure 15 shows a flowchart illustrating the overall process in the motor control method of this embodiment described above.

[0106] The configuration of the motor control method of this embodiment described above, and its effects, will now be explained.

[0107] In this embodiment, the first torque (gradient torque T) s ) is determined based on the longitudinal acceleration a1 of the electric vehicle and the rate of change of the vehicle speed parameter (vehicle speed V) that indicates the longitudinal velocity of the electric vehicle's body (vehicle acceleration a) (Equations 30 to 32).

[0108] In this way, by using the detection values ​​of the G-sensor and vehicle speed sensor that detect the actual longitudinal acceleration of the electric vehicle, the gradient torque T can be calculated in response to changes in driving resistance and changes in the driving force F acting on the vehicle body (such as brake operation) when driving uphill. s It can be set to an appropriate size.

[0109] Furthermore, in this embodiment, the second torque (acceleration torque T) acc ) and the temperature parameter (winding temperature T emp ) and gradient parameter (gradient torque T s Determined based on at least one of the following.

[0110] This results in a winding temperature T emp and / or depending on the magnitude of the gradient, an appropriate acceleration torque T acc This can be determined. More specifically, for example, the winding temperature T emp In situations where the acceleration torque T is relatively low, or where the gradient is relatively small, and there is little concern about excessive temperature rise within the motor control system, acc By setting this value relatively high, the driving performance of electric vehicles can be maintained more reliably.

[0111] Note that the winding temperature T emp and gradient torque T sIn place of, or in addition to, at least one of the above, the acceleration torque T is determined by referring to a vehicle speed parameter (such as the vehicle speed V above) that indicates the vehicle speed of the electric vehicle. acc A configuration that defines this may be adopted.

[0112] This allows for the second torque (acceleration torque T) to be appropriately adjusted according to the vehicle speed. acc ) can be determined. More specifically, for example, in the low vehicle speed region where the vehicle speed is below a certain level, the acceleration torque T acc By setting the acceleration torque relatively high, electric vehicles can smoothly merge into the flow of traffic during acceleration from a standstill (from a standstill to a constant speed). In addition, in the medium to high-speed range where the vehicle speed is above a certain level, the acceleration torque T acc By setting this value relatively low, excessive acceleration after transitioning from the low-speed range to the medium- and high-speed ranges can be suppressed, and excessive temperature rise within the motor control system can be controlled.

[0113] [Control results] In the following, the control results obtained by the motor control method (example) of the above embodiment will be explained in comparison with the control results obtained by the motor control method of the comparative example. Note that the comparative example differs from the control method of the embodiment in that it outputs the basic required torque T1 directly to the vibration damping control unit 36 ​​without performing the processing by the upper limit torque limit request determination unit 34 and the torque limit unit 35 shown in Figure 7 or Figure 10; however, the control method is assumed to be common to all other components.

[0114] Figure 16 is a graph showing the control results for the comparative example and the embodiment. In particular, Figure 16 assumes the control results when an electric vehicle continuously travels uphill for a predetermined period of time. Figure 16(a) shows the control results for the comparative example, and Figure 16(b) shows the control results for the embodiment.

[0115] As shown in the figure, in the control of the embodiment, the motor torque T after the start of limiting against the upper limit (t=t1) m The upward deviation is suppressed compared to the control in the comparative example. As a result, the winding temperature T in the example is suppressed. empThe maximum value of is decreased compared to that of the comparative example (indicated by the sign "ΔT" in the figure). emp (As shown in "[...]"). On the other hand, in the embodiment, although the vehicle speed after the start of the restriction (t=t1) is slightly lower than in the comparative example, it is maintained within a range that does not impair the driving performance required when driving on an uphill road.

[0116] Therefore, the control method in this embodiment achieves both ensuring driving performance when driving on uphill roads and suppressing excessive temperature rise.

[0117] Although embodiments of the present invention have been described above, the configurations described in the above embodiments and each of the modifications represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0118] For example, in each of the above embodiments, the winding temperature T detected by the thermistor 23 is used as a temperature parameter that indicates the temperature within the motor control system. emp An example of adopting this has been explained. However, the temperature parameter is not limited to this, and any other parameter can be adopted as long as it can indicate the temperature change within the motor control system in accordance with the magnitude of the gradient of the uphill road. For example, the temperature parameter may be the magnet temperature of the electric motor 5, the temperature of the power semiconductor element in the PWM inverter 4, and / or the temperature of the battery 1.

[0119] Furthermore, the configurations of the first and second embodiments may be combined as appropriate, provided they do not contradict each other. For example, the winding temperature T described in the second embodiment. emp , gradient torque T s , and variable acceleration torque T based on at least one of the vehicle speed V acc The calculation logic that determines the fixed acceleration torque T described in the first embodiment is used. acc The motor control method of the first embodiment may be applied by substituting the calculation logic that defines the gradient torque T described in the second embodiment. s The estimation logic for the disturbance torque T described in the first embodiment is used. d From gradient torque T sThe motor control method of the first embodiment may be applied by substituting the calculation logic that defines the function.

Claims

1. A motor control method for an electric vehicle equipped with an electric motor as a drive source, which controls the operation of the electric motor based on a predetermined higher-level required torque, The basic required torque is calculated from the aforementioned higher required torque, as well as the maximum and minimum torques of the electric motor. Obtain the gradient parameter a disturbance torque that includes the effect of the road surface gradient, or a gradient acceleration that corresponds to the effect of gravitational acceleration corresponding to the road surface gradient. From the gradient parameters, a first torque is calculated that is necessary to counteract the rollback force acting on the electric vehicle on an uphill road and maintain the vehicle speed at zero. The temperature of the stator winding of the electric motor, the magnet temperature of the electric motor, the temperature of the power semiconductor elements in the PWM inverter connected to the electric motor, and / or the temperature of the battery connected to the electric motor via the PWM inverter are acquired as temperature parameters. If the first torque and the temperature parameter are each above a predetermined threshold, a torque limiting process is performed to calculate the limited required torque as the smaller of the basic required torque and a predetermined correction torque upper limit. Based on the limited required torque, the electric motor is operated. In the torque limiting process described above, The correction torque upper limit is calculated from the first torque and the second torque, The second torque is defined as the torque that gives the electric vehicle a predetermined acceleration. Motor control method.

2. A motor control method according to claim 1, The disturbance torque as the gradient parameter is The calculation is performed as the difference between the estimated torque obtained by filtering the angular velocity of the electric motor and the reference torque based on the feedback value of the limited-request torque. Motor control method.

3. A motor control method according to claim 1, The gradient acceleration as the gradient parameter is The calculation is performed based on the longitudinal acceleration of the electric vehicle detected by the longitudinal acceleration sensor and the longitudinal speed of the electric vehicle's body detected by the vehicle speed sensor. Motor control method.

4. A motor control method according to any one of claims 1 to 3, The second torque is Determined based on at least one of the temperature parameter, the longitudinal speed of the electric vehicle detected by the vehicle speed sensor, and the first torque, Motor control method.

5. A motor control method according to claim 1, When the longitudinal speed of the electric vehicle detected by the vehicle speed sensor falls outside a predetermined vehicle speed range, Regardless of the relationship between the first torque and the temperature parameter and their respective predetermined thresholds, the smaller of the basic required torque and the upper limit of the corrected torque is calculated as the limited required torque, or The second torque is adjusted to increase the upper limit of the correction torque. Motor control method.

6. A motor control method according to claim 1, If the aforementioned basic required torque is less than a predetermined torque threshold, Regardless of the relationship between the gradient parameter and the temperature parameter and their respective predetermined thresholds, the smaller of the basic required torque and the upper limit of the corrected torque is calculated as the limited required torque, or The second torque is adjusted to increase the upper limit of the correction torque. Motor control method.

7. A motor control device for an electric vehicle equipped with an electric motor as a drive source, which controls the operation of the electric motor based on a predetermined higher-required torque, A basic required torque calculation unit calculates a basic required torque from the above-mentioned higher required torque and the maximum and minimum torques of the electric motor, A gradient parameter acquisition unit acquires a gradient parameter that includes a disturbance torque that includes the effect of the road surface gradient or a gradient acceleration that corresponds to the effect of gravitational acceleration corresponding to the road surface gradient, A first torque calculation unit calculates, from the gradient parameters, the first torque necessary to counteract the rollback force acting on the electric vehicle on an uphill road and maintain the vehicle speed at zero, A temperature parameter acquisition unit that acquires the temperature of the stator winding of the electric motor, the magnet temperature of the electric motor, the temperature of the power semiconductor elements in the PWM inverter connected to the electric motor, and / or the temperature of the battery connected to the electric motor via the PWM inverter as temperature parameters, A torque limiting unit that performs a torque limiting process when the first torque and the temperature parameter are each above a predetermined threshold, calculates the smaller of the basic required torque and a predetermined correction torque upper limit as the limited required torque, The electric motor has a control unit that operates the electric motor based on the limited required torque, The torque limiting unit is The correction torque upper limit is calculated from the first torque and the second torque, The second torque is defined as the torque that gives the electric vehicle a predetermined acceleration. Motor control device.

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