Motor torque zero-crossing control method of electric automobile
Through real -time detection of motor output torque and controlling motor output torque in stages, the impact and noise problems of the motor torque caused by the motor side of the electric vehicle due to the tooth gap, and improved the smooth driving.
Patent Information
- Application Number
- CN202411474500.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-22
- Publication Date
- 2025-01-21
AI Technical Summary
During the driving process, electric vehicles produce shocks and noises during the zero-crossing of the motor torque caused by the tooth side clearance, which affects the comfort and power smoothness of the vehicle.
Through real -time detection of motor output torque, determine whether the torque is excessive to activate, and divided into four stages of controlling motor output torque: slowly change to zero, first torque acceleration, second torque deceleration, and set the torque to catch up with the target torque.
It effectively avoids impact and noise, improves the driving smoothness during driving, and solves the impact and noise phenomenon when the motor torque crosses zero.
Smart Images
Figure CN119329316A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of new energy vehicle motor control, and in particular relates to a motor torque zero-crossing control method for an electric vehicle. Background Art
[0002] Electric vehicles use motors to drive wheels to achieve vehicle travel. The typical transmission system includes motors, reducers, differentials, half shafts, and wheels. During the torque transmission process, affected by the tooth side clearance, when the driving condition and the braking condition are switched, the meshing surface of the gear transmission changes. The driving wheel will undergo a short acceleration and then hit the meshing surface, resulting in a large impact and noise, and even causing the vehicle to shake, seriously affecting the comfort and power smoothness of the vehicle.
[0003] In order to solve the impact noise problem caused by tooth side clearance when accelerating or releasing the accelerator during driving, the commonly used method is to reduce the response rate of the motor's zero torque and limit the slope during the torque rise process; at the same time, the torque is maintained near zero torque to ensure torque transmission after the master and driven gears are fully engaged.
[0004] The above method requires many parameters to be adjusted and confirmed, and requires a lot of time and resources for actual vehicle debugging. At the same time, this method will cause the vehicle to respond slowly to the driver's quick accelerator operation, which does not meet driving expectations and affects the driver's driving experience. Summary of the invention
[0005] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and to provide a motor torque zero-crossing control method for an electric vehicle to improve the impact and noise phenomenon during the motor torque zero-crossing process.
[0006] The technical solution adopted by the present invention is: a motor torque zero-crossing control method for an electric vehicle, which detects the motor output torque in real time, and determines whether the motor torque zero-crossing function is activated based on the motor output torque. If the motor torque zero-crossing function is activated, the following stages are executed in sequence:
[0007] In the first stage, the actual output torque of the motor is controlled to change slowly until the actual output torque of the motor is 0;
[0008] In the second stage, the actual output torque of the motor is controlled to be the first torque, which lasts for a first set time;
[0009] In the third stage, the actual output torque of the motor is controlled to be a second torque, which lasts for a second set time, and the second set time is equal to the first set time;
[0010] In the fourth stage, the actual output torque of the motor is controlled to catch up with the set torque slope until the actual output torque of the motor is equal to the target torque of the motor.
[0011] Further, the process of judging whether the motor torque zero-crossing function is activated based on the motor output torque is as follows:
[0012] Set the torque zero-crossing activation interval to [-T act ,T act ], T act >0,T act To set the torque limit;
[0013] If the motor output torque changes from negative torque to positive torque, then when the motor output torque passes -T act At the moment, it is judged that the torque zero-crossing function is activated;
[0014] If the motor output torque changes from positive torque to negative torque, then when the motor output torque passes T act At the moment when the torque zero crossing function is judged to be activated.
[0015] Furthermore, the actual output torque of the motor in the first stage is determined by the following formula:
[0016] T1(t)=k*T0(t),
[0017] Wherein, T1(t) is the actual output torque of the motor at time t, T0(t) is the target torque of the motor at time t, k is the mitigation coefficient, 0<k<1.
[0018] Further, the process of determining the first torque is:
[0019] If the motor output torque changes from negative torque to positive torque, the first torque T1 is T1=T ref1 ;
[0020] If the motor output torque changes from positive torque to negative torque, the first torque T1 is T1 = -T ref1 ;
[0021] Among them, T ref1 is the rated torque, T ref1 Greater than the motor assembly drag torque T drag .
[0022] Furthermore, the first set time is equal to the second set time.
[0023] Furthermore, the first set time is determined by the following formula:
[0024]
[0025] a1=T0 / J
[0026] Among them, θ is the clearance of the vehicle transmission system,a1 is the acceleration of the driving gear, t1 is the first set time, T0 is the acceleration torque of the driving gear, and J is the rotational inertia of the motor rotor.
[0027] Furthermore, the process of determining the clearance of the vehicle transmission system is as follows:
[0028] The vehicle is stationary, the vehicle handbrake function is activated, the motor is controlled to output +10Nm and -10Nm in sequence, and the motor rotor position is recorded as θ respectively. a and θ b , then the vehicle transmission system clearance θ is θ=|θ a -θ b |.
[0029] Furthermore, the acceleration torque of the driving gear is determined by the following formula:
[0030] T0=T ref1 -T drag
[0031] Among them, T0 is the acceleration torque of the driving gear, T ref1 is the first torque, T drag is the drag torque of the motor assembly.
[0032] Furthermore, the process of determining the drag torque of the motor assembly is as follows:
[0033] In hot and cold environments respectively, the motor assembly is controlled to output different speeds, the drag torques at different speeds are tested, and the average value of all the drag torques is calculated as the drag torque of the motor assembly.
[0034] Furthermore, the process of determining the second torque is:
[0035] If the motor output torque changes from negative torque to positive torque, the second torque T2 is T2=2*T drag -T ref1 ;
[0036] If the motor output torque changes from positive torque to negative torque, the first torque T2 is T2=T ref1 -2*T drag ;
[0037] Among them, T ref1 is the rated torque, T drag is the drag torque of the motor assembly.
[0038] The beneficial effects of the present invention are:
[0039] The present invention monitors the output torque of the vehicle motor. When the motor output torque meets the preset zero-crossing control condition, the motor output acceleration and deceleration torque is controlled so that the master and driven gears are first accelerated and then decelerated. When the master and driven gear pairs are engaged, the relative speed between the master and driven gears is zero. At this time, applying the driving torque will no longer generate impact and noise, thereby improving the driving smoothness during driving, thereby solving the impact and noise phenomenon during the motor torque zero-crossing process. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Figure 1 It is a control flow chart of the present invention.
[0041] Figure 2 This is a curve showing the change of torque from a negative value to a positive value when the torque of the motor of the present invention passes through zero.
[0042] Figure 3 It is a schematic diagram of the change of the torque and angular velocity of the driving gear in different side tooth movements when the torque of the motor of the present invention changes from a negative value to a positive value when the torque passes through zero.
[0043] Figure 4 This is a curve showing the change of torque from a positive value to a negative value when the torque of the motor of the present invention passes through zero. DETAILED DESCRIPTION
[0044] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0045] like Figure 1 As shown, the present invention provides a motor torque zero-crossing control method for an electric vehicle, determines motor-related parameters, detects the motor output torque in real time, and determines whether the torque zero-crossing function is activated based on the motor output torque. If the torque zero-crossing function is activated, the following stages are performed in sequence:
[0046] In the first stage, that is, before the motor output torque passes through zero, the actual output torque of the motor is controlled to change slowly until the actual output torque of the motor is 0.
[0047] In the second stage, the actual output torque of the motor is controlled to be the first torque, which lasts for a first set time.
[0048] That is, when zero torque is just reached, the transmission gear pair is fully meshed on one side, and the relative speed between the master and driven gears is 0. At this time, the drive motor is controlled to output a reverse torque (i.e., the first torque, which is opposite to the torque direction before crossing zero), so that the driving gear rotates across the gap of the vehicle transmission system to the other side and accelerates. The angle of rotation of the driving gear is half of the gap of the vehicle transmission system (i.e., θ / 2) as the control target, and the action time t1 of the first torque is determined.
[0049] In the third stage, when the driving gear rotates at an angle of θ / 2, the actual output torque of the control motor is the second torque, so that the driving gear immediately obtains a reverse deceleration torque for a second set time, wherein the second torque is in the same direction as the first torque, and the second torque absolute value is less than the first torque absolute value, and the second set time is equal to the first set time, then the driving gear rotates at an angle of θ / 2 at the end of this stage. That is, the angle rotated in the second and third stages is θ, and the speed increment of the driving gear is 0.
[0050] The second stage and the third stage are the process in which the motor output torque first increases and then decreases when the torque passes through zero; the first set time and the second set time are determined by the motor related parameters;
[0051] In the fourth stage, the actual output torque of the motor is controlled to catch up with the set torque slope (that is, the actual output torque of the motor increases linearly with the set torque step) until the actual output torque of the motor is equal to the target torque of the motor. The starting moment of the fourth stage is the moment when the engagement of the master and driven gear pairs is completed and the relative speed between the master and driven gears is zero.
[0052] The present invention monitors the output torque of the vehicle motor. When the motor output torque meets the preset zero-crossing control condition, the motor output torque is controlled to increase first and then decrease, so that the driving gear is accelerated first and then decelerated. When the meshing of the master and driven gear pairs is completed, the relative speed between the master and driven gears is zero. At this time, applying the driving torque will no longer generate impact and noise, thereby improving the driving smoothness during driving, thereby solving the impact and noise phenomenon during the zero-crossing process of the motor torque.
[0053] The relevant parameters of the above-mentioned motors include three key parameters: the drag torque of the motor assembly, the clearance of the vehicle transmission system, and the rotational inertia of the motor rotor.
[0054] Motor assembly drag torque T drag The determination process is as follows: the drag torque test conditions are respectively in hot and cold environments, controlling the motor assembly to output different speeds, testing the drag torque at different speeds, and calculating the average value of all drag torques as the drag torque of the motor assembly. The specific working conditions are shown in Table 1.
[0055] Table 1 Drag torque test conditions
[0056]
[0057] The process of determining the clearance of the vehicle transmission system is as follows: the vehicle is stationary, the vehicle handbrake function is activated, and the vehicle motor is controlled by the motor controller to output +10Nm and -10Nm in sequence. At this time, the position information collected by the motor rotor position sensor is read as θ a and θ b , then the vehicle transmission system clearance θ is θ=|θ a -θ b |.
[0058] The motor rotor moment of inertia J can be obtained from the motor hardware design parameters.
[0059] During vehicle operation, the torque change trend of the motor may be from negative torque to positive torque, or from positive torque to negative torque. Therefore, the motor torque zero crossing includes the zero crossing of the motor torque in the process of changing from negative torque to positive torque and the zero crossing of the motor torque in the process of changing from positive torque to negative torque. These two torque change trends are described separately.
[0060] Example 1
[0061] like Figure 2 As shown, when the motor torque changes from negative torque to positive torque, the torque zero-crossing control process includes the following steps:
[0062] Step 1: Determine whether the torque zero-crossing function is activated.
[0063] Set the torque zero-crossing activation interval to [-T act ,T act ], T act >0,T act To set the torque limit. During the driving process, obtain the real-time monitoring data of the vehicle dynamics, that is, the motor output torque, and make an activation judgment on the torque zero crossing function based on the motor output torque and the preset torque zero crossing activation interval. When the drive motor torque changes from negative torque to positive torque, there is a trend of zero torque and after -T act The torque zero crossing function is activated when
[0064] Step 2: Determine the actual output torque and action time of the motor after zero-crossing activation.
[0065] In this embodiment, after the torque zero-crossing function is activated, the actual output torque change of the motor includes three stages, namely, the output torque reduction stage before the torque zero-crossing, the output torque increase stage after the zero-crossing, and the output torque reduction stage. The torque change after the zero-crossing corresponds to the process of the master and slave gear pairs accelerating first and then decelerating. The three stages of the actual output torque change of the motor are as follows:
[0066] 2.1. Slow down the output torque stage.
[0067] Before the torque passes through zero, the driven gear gradually fits the driving gear. During the process of the motor torque changing from negative to positive, the driving gear torque gradually decreases to the reverse direction. At this time, the torque of the driving gear is a resistance to the driven gear, and the total force received by the driven gear will become larger and larger. Therefore, before passing through zero, if the motor output torque follows the motor target torque unchanged, that is, the driving gear still decreases too fast according to the original torque change, the speed of the driven gear will suddenly increase, and the wheel speed will also suddenly change, and the whole vehicle will feel bad. In response to this problem, this embodiment slows down the torque output before the torque zero-crossing function is activated and the motor output torque has not reached zero torque, that is, when it is below 0Nm, the actual output torque of the motor is controlled to change slowly until the actual output torque of the motor is 0, which can effectively slow down the sudden change of vehicle speed and improve the driving experience.
[0068] Specifically, the actual output torque of the motor at this stage is determined by the formula: T1(t)=k*T0(t), where T1(t) is the actual output torque of the motor at time t, T0(t) is the target torque of the motor at time t, and k is the mitigation coefficient, 0<k<1, to slow down the zero-crossing torque output slope.
[0069] 2.2, increasing the output torque stage, such as Figure 3 As shown, when the motor output torque reaches zero torque value, the driving gear and the driven gear are in a one-side gear state, and the relative speed between them is 0. At this time, the vehicle motor controller controls the motor to output the first torque T1, and lasts for the first set time t1, T1 = T ref1 , T ref1 is the rated torque and T ref1 >T drag , the first output torque is opposite to the output torque before zero crossing.
[0070] After the first torque output by the motor overcomes the internal drag torque of the motor, the acceleration torque of the driving gear is T0 = T ref1 -T drag Since T0>0, the driving gear accelerates. At this time, the acceleration of the driving gear is a1=T0 / J. The driving gear maintains the acceleration of a1 and rotates through the angle at this time The first set time t1 required for the first torque to act can be calculated. At the end of the acceleration phase, the angular velocity of the driving wheel is
[0071] 2.3, in the post-torque reduction stage, after the motor outputs the first torque for a first set time, the motor is controlled to output the second torque T2, so that the driving torque obtained by the active gear end is T a = - T0 = T2 - T drag , then T2=2*Tdrag -T ref 1 ; Due to T a <0, at this time the driving gear performs deceleration motion, and the acceleration is calculated as a2 = -T0 / J = -a1, so that it rotates through an angle θ2 = θ - θ1 = θ / 2, that is Calculation shows that t1=t2, t0=t1+t2. At the end of the deceleration phase, the angular velocity of the driving wheel is:
[0072]
[0073] In practice, the time it takes for the active gear to complete the acceleration and deceleration is extremely short, and the speed change of the driven gear during this stage can be ignored. Figure 2 At point A in the figure, the driving and driven gears have completed meshing and the relative speed between them is zero, completing a smooth transition between the different side teeth.
[0074] Step 3: The actual output torque of the motor catches up with the target torque of the motor
[0075] Due to the existence of the motor zero-crossing control function, at point A, there is a large difference between the actual output torque of the motor and the target torque of the motor. Therefore, after completing the different side tooth movements, the target torque of the motor needs to be caught up. According to the calibrated set torque slope, the actual output torque of the motor is controlled by the motor controller to execute according to the set torque slope (that is, the actual output torque is controlled to change according to the specified torque step) until it catches up with the motor target torque value, that is, the entire motor torque zero-crossing control process is completed. The set torque slope needs to be within an appropriate range to ensure that the driver does not feel a delay in the power response during the torque catching-up process (because the catching-up slope is too small, the catching-up time is too long, and the response is delayed), and there is no impact (the catching-up slope is too large, and the acceleration mutation is large). The set torque slope is preferably 20-50Nm / ms, and can be specifically 30Nm / ms or 40Nm / ms.
[0076] Example 2
[0077] like Figure 4 As shown in FIG. 1 , when the motor torque changes from positive torque to negative torque, the torque zero-crossing control process includes the following steps:
[0078] Step 1: Determine whether the torque zero-crossing function is activated.
[0079] Set the torque zero-crossing activation interval to [-T act ,T act ], T act >0,T actTo set the torque limit. During the driving process, obtain the real-time monitoring data of the vehicle dynamics, that is, the motor output torque, and make an activation judgment on the torque zero crossing function based on the motor output torque and the preset torque zero crossing activation interval. When the drive motor torque changes from positive torque to negative torque, has a tendency to cross zero torque and passes through T act The torque zero crossing torque function is activated.
[0080] Step 2: Determine the actual output torque and action time of the motor after zero-crossing activation.
[0081] The change process and action time of the actual output torque of the motor in this step are basically the same as those in Example 1. The difference is that the change trend of the motor output torque is from positive to negative, which is opposite to Example 1. Therefore, the torque change process in each stage is the same as that in Example 1, but the direction is completely opposite, and will not be described in detail here.
[0082] Step 3: The actual output torque of the motor catches up with the target torque of the motor
[0083] After completing different side tooth movements, the target torque needs to be caught up and the size of the catching-up torque slope is determined to ensure that the actual output torque of the motor catches up with the motor target torque within a reasonable time.
[0084] By implementing the electric vehicle motor torque zero-crossing control method of the present invention, impact and tooth knocking caused by tooth gaps between gears, splines and other components of the electric vehicle power transmission are avoided, thereby improving the smoothness of vehicle driving and enhancing comfort.
[0085] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.
Claims
1. A method for controlling the zero-crossing torque of a motor of an electric vehicle, characterized in that: The motor output torque is detected in real time. Based on the motor output torque, it is determined whether the torque zero-crossing function is activated. If the torque zero-crossing function is activated, the following stages are executed in sequence: In the first stage, the actual output torque of the motor is controlled to change slowly until the actual output torque of the motor is 0; In the second stage, the actual output torque of the motor is controlled to be the first torque, which lasts for a first set time; In the third stage, the actual output torque of the motor is controlled to be the second torque, which lasts for a second set time; In the fourth stage, the actual output torque of the motor is controlled to catch up with the set torque slope until the actual output torque of the motor is equal to the target torque of the motor.
2. The motor torque zero-crossing control method of an electric vehicle according to claim 1, characterized in that: The process of judging whether the torque zero-crossing function is activated based on the motor output torque is as follows: Set the torque zero-crossing activation interval to [-T act ,T act ], T act >0,T act To set the torque limit; If the motor output torque changes from negative torque to positive torque, then when the motor output torque passes -T act At the moment, it is determined that the torque zero-crossing function is activated; If the motor output torque changes from positive torque to negative torque, then when the motor output torque passes T act At the moment when the torque zero-crossing function is judged to be activated.
3. The motor torque zero-crossing control method of an electric vehicle according to claim 1, characterized in that: The actual output torque of the motor in the first stage is determined by the following formula: T1(t)=k*T0(t), Wherein, T1(t) is the actual output torque of the motor at time t, T0(t) is the target torque of the motor at time t, k is the mitigation coefficient, 0<k<1.
4. The method for controlling the motor torque zero crossing of an electric vehicle according to claim 1, characterized in that: The process of determining the first torque is: If the motor output torque changes from negative torque to positive torque, the first torque T1 is T1= Tref1 ; If the motor output torque changes from positive torque to negative torque, the first torque T1 is T1 = - Tref1 ; Among them, T ref1 is the rated torque, T ref1 Greater than the motor assembly drag torque T drag .
5. The motor torque zero-crossing control method of an electric vehicle according to claim 1, characterized in that: The first set time is equal to the second set time.
6. The method for controlling the motor torque zero crossing of an electric vehicle according to claim 5, characterized in that: The first set time is determined by the following formula: a1=T0 / J Among them, θ is the clearance of the vehicle transmission system, a1 is the acceleration of the driving gear, t1 Set the time for the first time, T0 is the acceleration torque of the driving gear, J is the motor rotor moment of inertia.
7. The method for controlling the motor torque zero crossing of an electric vehicle according to claim 6, characterized in that: The process of determining the clearance of the vehicle transmission system is as follows: The vehicle is stationary, the vehicle handbrake function is activated, the motor is controlled to output +10Nm and -10Nm in sequence, and the motor rotor position is recorded as θ respectively. a and θ b , then the vehicle transmission system clearance θ is θ＝ | θa－θb |.
8. The method for controlling the motor torque zero crossing of an electric vehicle according to claim 6, characterized in that: The acceleration torque of the driving gear is determined by the following formula: T0=T ref1 -T drag in, T0 is the acceleration torque of the driving gear, Tref1 For the rated torque, Tdrag is the drag torque of the motor assembly.
9. The method for controlling the motor torque zero crossing of an electric vehicle according to claim 8, characterized in that: The process of determining the drag torque of the motor assembly is as follows: In hot and cold environments respectively, the motor assembly is controlled to output different speeds, the drag torques at different speeds are tested, and the average value of all the drag torques is calculated as the drag torque of the motor assembly.
10. The motor torque zero-crossing control method of an electric vehicle according to claim 1, characterized in that: The process of determining the second torque is: If the motor output torque changes from negative torque to positive torque, the second torque T2 is T2=2*T drag -T ref1 ; If the motor output torque changes from positive torque to negative torque, the first torque T2 is T2=T ref1 -2 * T drag ; in, Tref1 For the rated torque, Tdrag is the drag torque of the motor assembly.