A method and system for zero-torque control of an electric vehicle

Abstract

This invention discloses a method for controlling the torque zero-crossing of an electric vehicle, comprising the following steps: Step 1, acquiring the operation information input by the driver; Step 2, calculating the vehicle's driving torque demand based on the operation information; Step 3, acquiring vehicle information and limiting the torque demand based on the vehicle information; Step 4, sending the limited vehicle driving torque demand to the MCU and braking system for execution. This invention's method for controlling the torque zero-crossing of new energy vehicles aims to improve the user experience when the torque crosses zero, enhancing driving smoothness through a closed-loop process of "calibration-verification-optimization".

Description

Technical Field

[0001] This invention relates to the field of electric vehicle power control technology. Background Technology

[0002] With social progress, new energy vehicles are increasingly becoming an important means of transportation. However, because they lack the idling characteristics of traditional fuel vehicles, drivers need to frequently switch between the accelerator and brake pedals when following other vehicles at low speeds, which affects the smoothness and comfort of driving.

[0003] To alleviate driving fatigue under low-speed conditions, the commonly used technical solution is to have the vehicle control unit (VCU) actively request drive torque when the vehicle is powered on and in a specific low-speed range in D or R gear, simulating the idling behavior of a gasoline vehicle. This function is usually called "crawl mode". For example, the published document with authorization announcement number CN110803031B and patent title "A Method for Controlling Parking, Crawl, and Crawl Speed ​​Limiting of Electric Vehicles" discloses the following method: When the handbrake signal is 0 and the gear is not in neutral, the VCU sends a parking command to the MCU. The MCU determines whether to enter the parking mode and controls the motor to achieve the parking function. When the vehicle is in parking mode, if the difference between the torque sent by the VCU to the MCU and the actual parking torque of the MCU exceeds a preset threshold, the parking mode is released. The VCU sets crawling conditions and crawling speed limit conditions based on the vehicle speed, handbrake status, and accelerator and brake pedal status. When all crawling conditions are met, the crawling mode is entered. The VCU calculates the crawling torque and sends it to the MCU. The MCU controls the motor to run based on the received crawling torque. When all crawling speed limit conditions are met, the crawling speed limit mode is entered; otherwise, the crawling speed limit mode is released.

[0004] However, during crawling, the vehicle often operates near zero torque. Affected by torque following error and fluctuations in driving resistance, the drive gear of the drive motor and the driven gear of the reducer are prone to repeated disengagement and engagement, which in turn generates tooth surface impact noise. This has an adverse effect on the noise, vibration and harshness (NVH) performance of the whole vehicle, reducing the driving quality experience.

[0005] Therefore, how to accurately control the gradient of torque at zero crossing through the vehicle control unit (VCU) in order to improve the impact phenomenon of the vehicle under zero crossing conditions has become a key technical problem that needs to be solved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to realize a method and system for controlling the torque zero crossing stage with precision, thereby improving the impact phenomenon of the whole vehicle under the zero crossing condition.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for controlling the zero-crossing torque of an electric vehicle, comprising the following steps:

[0008] Step 1: Obtain the operation information input by the driver;

[0009] Step 2: Calculate the vehicle's drive torque requirement based on the operation information;

[0010] Step 3: Obtain vehicle information and limit torque requirements based on the vehicle information;

[0011] Step 4: Send the limited vehicle drive torque requirement to the MCU and braking system for execution.

[0012] In step 1, the operation information input by the driver includes the accelerator pedal, brake pedal, and desired vehicle speed.

[0013] Based on different driving modes, select the corresponding preset pedal torque MAP for that driving mode.

[0014] In step 2, the vehicle drive torque requirement is obtained based on the calibrated initial torque MAP.

[0015] In step 3, the vehicle information includes vehicle speed, battery SOC, maximum battery charging / discharging power, and maximum motor input / output power.

[0016] In step 3, limiting the torque demand includes adjusting the filter coefficient and activating the anti-shake adjustment calibration, and has a mode-differentiated MAP generated by adjusting the filter coefficient and activating the anti-shake adjustment calibration.

[0017] The activated anti-shake adjustment calibration is based on the dynamic adjustment of the existing pedal torque MAP, which reduces the slope of the pedal requested torque change by 40%–60% in the ±20Nm torque zero-crossing region to mitigate torque response;

[0018] The adjustment of the filter coefficient is based on the required torque T_req, where the filter duration is selected. When |T_req| ≤ 10Nm, a filter duration of 0.5s is used, and when |T_req| > 10Nm, a filter duration of 0.2s is used.

[0019] When the torque output is zero, it is determined that the torque direction is switching. First, a zero torque request is output for 100–200ms to eliminate the backlash in the transmission system, and then the torque is smoothly transitioned to the target torque.

[0020] In step 4, the vehicle driving torque is obtained based on the mode differentiation MAP.

[0021] The electric vehicle torque zero-crossing control method starts optimization when the vehicle detects uneven driving or knocking sounds, and executes the optimized mode differentiation MAP after the optimization is completed.

[0022] An electric vehicle torque zero-crossing control system is provided. The system is equipped with a VCU, which is connected to a CAN bus to obtain the driver's input operation information and vehicle information. The VCU is connected to and outputs torque demand to the MCU and the braking system. The system executes the electric vehicle torque zero-crossing control method.

[0023] The VCU has a functional module for executing the electric vehicle torque zero-crossing control method:

[0024] Braking control module: Obtains braking torque distribution based on braking status or kinetic energy recovery status, and outputs motor braking torque data based on braking torque distribution status to torque coordination module;

[0025] Drive control module: Calculates the drive torque limit based on the drive torque demand, and outputs motor drive torque data to the torque coordination module based on the drive torque limit status;

[0026] Torque Coordination Module: Integrates motor braking torque data and motor drive torque data to obtain torque zero-crossing limit and torque slope control, and outputs motor torque request.

[0027] This invention relates to a method for controlling the zero-crossing torque of new energy vehicles, which aims to improve the user experience when the torque crosses zero by enhancing driving smoothness through a closed-loop process of "calibration-verification-optimization".

[0028] First, the torque output curves (pedal MAP) of the accelerator pedal are calibrated for different driving modes. During actual testing, if uneven acceleration or knocking sounds are detected, the torque output curves and related filtering parameters are optimized. If the jolt persists, the system activates the anti-shake function, automatically adjusting the torque filtering parameters to adaptively suppress vibrations, ultimately achieving a smoother and more comfortable driving experience. Attached Figure Description

[0029] The following is a brief explanation of the content represented by each figure in this specification:

[0030] Figure 1 This is a structural diagram of an electric vehicle torque zero-crossing control system.

[0031] Figure 2 This is a flowchart of a method for controlling the torque zero crossing of an electric vehicle. Detailed Implementation

[0032] The following description, with reference to the accompanying drawings, details the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0033] In current new energy vehicles, the vehicle often operates near zero torque when driving at low speeds. Due to torque following error and fluctuations in driving resistance, the drive gear of the drive motor and the driven gear of the reducer are prone to repeated disengagement and engagement, which generates tooth surface impact noise. This adversely affects the noise, vibration, and harshness (NVH) performance of the entire vehicle, reducing the driving quality experience.

[0034] Therefore, this design invented a method for controlling the torque zero crossing of new energy vehicles. By calibrating the MAP of "accelerator pedal opening - demand torque" under different driving modes, the problem of zero crossing knock and start-up vibration is improved, thereby enhancing the user's driving experience.

[0035] like Figure 1 As shown, the electric vehicle torque zero-crossing control system includes a VCU (Vehicle Control Unit). The VCU connects to the CAN bus to obtain driver input and vehicle information. The VCU connects to and outputs torque demand to the MCU (Microcontroller Unit) and the braking system. The system executes the electric vehicle torque zero-crossing control method. The VCU is the control core of the entire system. In order to achieve electric vehicle torque zero-crossing control, it has the following functional modules:

[0036] Braking control module: Obtains braking torque distribution based on braking status or kinetic energy recovery status, and outputs motor braking torque data based on braking torque distribution status to torque coordination module;

[0037] Drive control module: Calculates the drive torque limit based on the drive torque demand, and outputs motor drive torque data to the torque coordination module based on the drive torque limit status;

[0038] Torque Coordination Module: Integrates motor braking torque data and motor drive torque data to obtain torque zero-crossing limit and torque slope control, and outputs motor torque request.

[0039] The VCU's torque management method is as follows: Based on the input information such as the accelerator pedal, brake pedal, and required vehicle speed from the driver module, the vehicle's driving torque requirement is calculated. Combined with the vehicle speed, battery SOC, maximum battery charging / discharging power, and maximum motor input / output power, the required torque is limited and filtered. Finally, the torque requirement is sent to the MCU and braking system.

[0040] in:

[0041] 1. The vehicle is traveling at a speed greater than 1 km / h and the driver has depressed the brake pedal;

[0042] 2. The battery SOC and vehicle speed meet the following conditions: when the SOC is less than the recycling entry threshold and the recycling enable state is 0, or when the SOC is less than the recycling exit threshold and the recycling enable state is 1; when the vehicle speed is greater than the recycling entry threshold and the recycling enable state is 0, or when the vehicle speed is greater than the recycling exit threshold and the recycling enable state is 1.

[0043] 3. Required torque = Motor drive external characteristics * Accelerator pedal opening

[0044] 4. Calculate the maximum torque under the allowable power using the formula, and take the minimum value between this value and the motor's required torque:

[0045] 5. To prevent drive wheel slippage, the required torque of the motor needs to be further limited by the ground adhesion.

[0046] Torque zero-crossing control is mainly optimized for the drivability of vehicles. When the motor torque commutation is detected, its torque slope can be reduced, and a zero torque request can be sent within a certain period of time. The purpose is to allow the active dimension to engage with the driven wheel meshing surface at a slower speed.

[0047] The main control principle is based on the specific calibration and verification of the pedal torque MAP under different driving modes to achieve differentiated driving performance goals. Specifically: in Eco / Comfort mode, the system adopts a higher intervention intensity, prioritizing the smoothness of power output by enhancing filtering and limiting the torque change rate, thereby creating a relaxed and comfortable driving experience; while in Sport mode, the system reduces the degree of intervention, decreases the filtering intensity, and allows for faster torque response, retaining a moderate sense of impact within a reasonable range to improve driving participation and road feedback, meeting the user's expectations for power performance. During the calibration and verification process, if uneven driving or knocking sounds occur, the system will collaboratively optimize the pedal torque MAP and filtering parameters, achieving performance improvement through adaptive adjustment; if impact phenomena are still detected during dynamic operation, the anti-shake adjustment function will be further activated, and the torque filtering parameters will be adaptively adjusted, thereby continuously optimizing driving quality and ensuring that the vehicle can achieve a smooth and comfortable driving performance under various operating conditions.

[0048] To achieve scenario-based and adaptive intelligent adjustment, key parameters, including gear position, motor speed, and torque request, are monitored in real time to identify typical operating conditions that are prone to shock, such as "active gear engagement," "rapid acceleration," and "rapid deceleration." When "active gear engagement" is detected, the system employs a constant torque output strategy, using a preset torque as a stability benchmark to ensure smooth meshing of the transmission system and effectively suppress gear impact. Under "rapid acceleration / deceleration" conditions, the system activates anti-vibration control and adaptively adjusts torque filtering parameters based on the actual impact intensity, forming an intelligent buffer mechanism that achieves an optimal balance between smoothness and dynamic responsiveness.

[0049] This involves considering whether the vehicle is in an active gear engagement state. Based on the vehicle's current gear, motor speed, and requested torque, combined with preset speed and torque ranges, it's determined whether the vehicle is in an "active gear engagement state." If it is, the motor outputs a preset fixed torque; otherwise, the motor outputs the requested torque. The "active gear engagement state" is a condition where gear meshing impact may occur during vehicle operation. In this state, by controlling the motor to output stable torque, the impact between gears can be effectively mitigated, reducing operating noise and vibration, thereby improving the NVH (noise, vibration, and harshness) performance of electric vehicles at low speeds and further optimizing the driving experience.

[0050] Specific implementation: After the VCU detects relevant parameters such as vehicle speed, acceleration, and accelerator pedal opening, the smoothness of the torque zero-crossing condition is improved through the following collaborative control strategies: Dynamically adjust the torque MAP, reducing the slope of the pedal-requested torque change by 40%–60% within the ±20Nm torque zero-crossing region to mitigate torque response; Implement adaptive filtering optimization, selecting the filtering duration based on the absolute value of the required torque, using 0.5s filtering when |T_req| ≤ 10Nm and 0.2s filtering when |T_req| > 10Nm to suppress sudden torque signal changes; and Introduce zero-torque bridging control, when a torque direction change is detected, first output a zero-torque request for 100–200ms to eliminate transmission system backlash, and then smoothly transition to the target torque, thereby effectively improving driving quality and suppressing jerks and shocks.

[0051] The aforementioned torque zero-crossing control method for new energy vehicles can improve the zero-torque condition in creep mode. During creep mode, due to torque following errors and resistance changes, the drive gear of the drive motor and the driven gear of the reducer repeatedly disengage and mesh, generating tooth surface impact noise, affecting the vehicle's NVH (noise, vibration, and harshness) and the driver's driving experience. The vehicle control unit (VCU) of this invention monitors the dynamic response during the torque zero-crossing process based on real-time parameters such as vehicle speed, acceleration, and accelerator pedal opening. It dynamically adjusts the torque change slope by adjusting the accelerator pedal torque MAP and the torque filter MAP. During the torque zero-crossing phase, the system actively reduces the torque change gradient to alleviate transmission shock. Simultaneously, when a torque direction change is detected, the VCU will output a zero-torque request within a set time to eliminate mechanical backlash and ensure a smooth torque transition. This control strategy effectively improves the knocking noise and start-up vibration problems during the torque zero-crossing process, enhancing vehicle ride smoothness and driving quality.

[0052] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for zero-torque control of an electric vehicle, characterized in that, Includes the following steps: Step 1: Obtain the operation information input by the driver; Step 2: Calculate the vehicle's drive torque requirement based on the operation information; Step 3: Obtain vehicle information and limit torque requirements based on the vehicle information; Step 4: Send the limited vehicle drive torque requirement to the MCU and braking system for execution.

2. The electric vehicle torque zero crossing control method of claim 1, wherein: In step 1, the driver inputs the following operation information: accelerator pedal, brake pedal, and desired vehicle speed. Based on different driving modes, select the corresponding preset pedal torque MAP for that driving mode.

3. The electric vehicle torque zero crossing control method of claim 2, wherein: In step 2, the vehicle drive torque requirement is obtained based on the calibrated initial torque MAP.

4. The electric vehicle torque zero crossing control method of claim 1, 2 or 3, wherein: In step 3, the vehicle information includes vehicle speed, battery SOC, maximum battery charging / discharging power, and maximum motor input / output power.

5. The electric vehicle torque zero crossing control method of claim 4, wherein: In step 3, limiting the torque demand includes adjusting the filter coefficient and activating the anti-shake adjustment calibration, and has a mode-differentiated MAP generated by adjusting the filter coefficient and activating the anti-shake adjustment calibration.

6. The electric vehicle torque zero crossing control method of claim 5, wherein: The activated anti-shake adjustment calibration is based on the dynamic adjustment of the existing pedal torque MAP, which reduces the slope of the pedal requested torque change by 40%–60% in the ±20Nm torque zero-crossing region to mitigate torque response; The adjustment of the filter coefficient is based on the required torque T_req, where the filter duration is selected. When |T_req| ≤ 10Nm, a filter duration of 0.5s is used, and when |T_req| > 10Nm, a filter duration of 0.2s is used. When the torque output is zero, it is determined that the torque direction is switching. First, a zero torque request is output for 100–200ms to eliminate the backlash in the transmission system, and then the torque is smoothly transitioned to the target torque.

7. The electric vehicle torque zero crossing control method of claim 1 or 6, wherein: In step 4, the vehicle driving torque is obtained based on the mode differentiation MAP.

8. The electric vehicle torque zero crossing control method of claim 7, wherein: The electric vehicle torque zero-crossing control method starts optimization when the vehicle detects uneven driving or knocking sounds, and executes the optimized mode differentiation MAP after the optimization is completed.

9. An electric vehicle torque zero crossing control system, characterized by, The system is equipped with a VCU, which is connected to the CAN bus to obtain the driver's input operation information and vehicle information. The VCU is connected to and outputs the torque demand to the MCU and the braking system. The system executes the electric vehicle torque zero crossing control method as described in any of claims 1-8.

10. The electric vehicle torque zero crossing control system of claim 9, wherein: The VCU has a functional module for executing the electric vehicle torque zero-crossing control method: Braking control module: Obtains braking torque distribution based on braking status or kinetic energy recovery status, and outputs motor braking torque data based on braking torque distribution status to torque coordination module; Drive control module: Calculates the drive torque limit based on the drive torque demand, and outputs motor drive torque data to the torque coordination module based on the drive torque limit status; Torque Coordination Module: Integrates motor braking torque data and motor drive torque data to obtain torque zero-crossing limit and torque slope control, and outputs motor torque request.

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