Speed-following control strategy for new energy vehicle

Abstract

The invention discloses a speed-following control strategy for a new energy vehicle, and the strategy comprises the following steps: S1, collecting vehicle basic data which comprises a vehicle speed, a steering wheel angle, a motor real-time torque and a driver steering torque; s2, preprocessing the vehicle basic data based on an S-type function; s3, calculating a vehicle speed basic rotating speed, a torque coupling rotating speed and a dynamic safety rotating speed respectively; s4, forming a target rotating speed strategy and a rotating speed amplitude limiting strategy based on the vehicle speed basic rotating speed, the torque coupling rotating speed and the dynamic safe rotating speed; s5, establishing a steering wheel rotation angle dynamic compensation strategy based on the steering wheel rotation angle; s6, correcting or compensating the target rotating speed strategy and the rotating speed amplitude limiting strategy based on the steering wheel rotating angle dynamic compensation strategy; compared with the prior art, perfect balance between low-speed flexibility and high-speed stability of power-assisted steering is achieved through a nonlinear weight distribution mechanism, an electromechanical system energy cooperation equation, a fuzzy attenuation function and a dynamic differential compensation algorithm.

Description

Technical Field

[0001] The present invention relates to the field of new energy vehicle control, and in particular to a speed-dependent control strategy for new energy vehicles. Background Art

[0002] The electric hydraulic power steering pump provides power through an electric motor to help the driver easily control the steering wheel when necessary, especially when driving at low speeds or making emergency avoidance maneuvers. This assistance can significantly improve the stability and safety of the vehicle.

[0003] In emergency situations, such as when a vehicle encounters a breakdown or other unexpected situations and requires emergency steering, the electric hydraulic power pump can respond quickly and provide the necessary steering assistance, which is crucial to avoiding potential dangers. Therefore, the necessity of vehicles with electric hydraulic power pumps in emergency steering is self-evident. It can provide the driver with necessary support at critical moments to ensure driving safety.

[0004] The existing speed-dependent control strategy is incompatible with high-speed steering stability and low-speed steering flexibility, and the existing control strategy has problems such as high motor energy consumption and large path following error. Summary of the invention

[0005] The purpose of the present invention is to address the problem that the existing speed-dependent speed control strategy is incompatible with high-speed stability and low-speed flexibility. To address this deficiency, a speed-dependent speed control strategy for new energy vehicles is proposed.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A speed-dependent control strategy for new energy vehicles includes the following steps:

[0008] S1. Collect basic vehicle data, including vehicle speed V, steering wheel angle Lwis, motor real-time torque Tm and driver steering torque Ts;

[0009] S2, preprocessing vehicle basic data based on S-type function;

[0010] S3. According to

[0011] V1=(V_max-V) / V_max×α×N;

[0012] V2=β×(Ts×Lwis) / (Ts_max×Lwis_max)×N;

[0013] V3=γ×√(Tm^2+Ts^2) / √2×N / √(Tm_max^2+Ts_max^2);

[0014] Among them, V1 is the basic speed of the vehicle, V_max is the maximum speed of the vehicle, α∈[0.2,0.6] is the speed attenuation coefficient; V2 is the torque coupling speed, β is the dynamic coupling coefficient, β=tanh(0.01Tm), tanh is the hyperbolic tangent function; V3 is the dynamic safety speed, γ is the safety factor, Tm_max is the maximum motor real-time torque, Ts_max is the maximum driver steering torque, and N is the standard amplitude of the speed at static state;

[0015] Calculate the vehicle basic speed V1, torque coupling speed V2 and dynamic safety speed V3 respectively;

[0016] S4, forming a target speed strategy V_target and a speed limit strategy V_ehps based on the vehicle speed base speed V1, the torque coupling speed V2 and the dynamic safety speed V3;

[0017] S5, establishing a steering wheel angle dynamic compensation strategy ΔV based on the steering wheel angle Lwis;

[0018] S6. Based on the steering wheel angle dynamic compensation strategy, the target speed strategy V_target and the speed limit strategy V_ehps are corrected or compensated to obtain a new target speed strategy V_target' and a new speed limit strategy V_ehps'.

[0019] As a further preferred embodiment of the present invention, the target speed strategy V_target and the speed limit strategy V_ehps are respectively:

[0020] V_target=max(V1,V2,V3)×(1-0.2e^(-0.1V));

[0021] V_ehps=min(V_target,N)×SAT(Tm / Tm_limit);

[0022] Among them, SAT is the saturation function, Tm_limit is the maximum allowable torque of the motor, and N is the standard amplitude of the speed in static state.

[0023] As a further preference of the present invention, the dynamic compensation strategy ΔV is ΔV=k×d(Lwis) / dt×e^(-0.05V), wherein k is the compensation gain, d(Lwis) / dt represents the derivative of the steering wheel angle Lwis with respect to time t, that is, the instantaneous rate of change of the steering wheel angle, which is used to reflect how fast the driver turns the steering wheel.

[0024] As a further preferred embodiment of the present invention,

[0025]

[0026] As a further preferred embodiment of the present invention, the target speed strategy V_target and the speed limit strategy V_ehps are corrected based on the dynamic compensation strategy for the steering wheel angle, including:

[0027] S61. According to

[0028] V_target'=V_target+ΔV;

[0029] Modify the target speed strategy V_target to form a new target speed strategy V_target';

[0030] S62, according to

[0031] ΔVlimit=500·(1-e^-0.02∣d(Lwis) / dt∣)

[0032] The dynamic upper limit compensation ΔVlimit is calculated;

[0033] S63, according to

[0034] Vlimit′=N+ΔVlimit·SAT(Tm / Tm_limit),

[0035] Wherein, N is the standard amplitude of the speed in static state; the speed Vlimit′ upper limit is adjusted;

[0036] S64, according to

[0037] V_ehps'=min(V_target',V limit′ )×SAT(Tm / Tm_limit),

[0038] The speed limit strategy V_ehps is modified to form a new target speed strategy V_ehps'.

[0039] Compared with the prior art, the speed-dependent control strategy for new energy vehicles proposed in the present invention has the following beneficial effects:

[0040] 1. The present invention calculates the target speed strategy by combining the nonlinear weight distribution mechanism with the nonlinear attenuation related to the vehicle speed, which can monitor the design framework, realize the multi-condition adaptive power-assistance characteristics, and provide a basic framework for subsequent algorithm upgrades (such as dynamic compensation layer);

[0041] 2. The present invention realizes electromechanical torque synergy by introducing dynamic coupling coefficient and electromechanical system energy synergy equation;

[0042] 3. The present invention adopts the fuzzy attenuation function of vehicle speed, which can control the current vehicle more accurately;

[0043] 4. The present invention sets the safety factor and adopts fuzzy control for dynamic adjustment, which can better calculate the dynamic safety speed;

[0044] 5. The present invention adopts a dynamic differential compensation algorithm to fine-tune the steering strategy, achieving a perfect balance between the present invention and high-speed stability;

[0045] 6. The present invention introduces a vehicle speed index compensation term to optimize high-speed stability;

[0046] 7. The present invention adopts steering wheel angle differential compensation to optimize the dynamic response during sudden steering changes;

[0047] 8. The present invention adopts S-type function to smooth the signal, which can effectively eliminate sensor noise. DETAILED DESCRIPTION

[0048] The present invention is specifically described in detail with reference to the following specific embodiments.

[0049] A speed-dependent control strategy for new energy vehicles includes the following steps:

[0050] S1. Collect basic vehicle data, where the basic vehicle data includes: vehicle speed V, steering wheel angle Lwis, motor real-time torque Tm, and driver steering torque Ts.

[0051] S2, preprocessing vehicle basic data based on S-type function;

[0052] The basic vehicle data is normalized, that is, the S-type function is used to smooth the signal: X_norm = 1 / (1+e^(-k(x-x0))) to eliminate sensor noise.

[0053] S3. According to

[0054] V1=(V_max-V) / V_max×α×N;

[0055] V2=β×(Ts×Lwis) / (Ts_max×Lwis_max)×N;

[0056] V3=γ×√(Tm^2+Ts^2) / √2×N / √(Tm_max^2+Ts_max^2);

[0057] Among them, V1 is the basic speed of the vehicle, V_max is the maximum speed of the vehicle, α∈[0.2,0.6] is the speed attenuation coefficient; V2 is the torque coupling speed, β is the dynamic coupling coefficient, β=tanh(0.01Tm), tanh is the hyperbolic tangent function; V3 is the dynamic safety speed, γ is the safety factor, Tm_max is the maximum motor real-time torque, Ts_max is the maximum driver steering torque, and N is the standard amplitude of the speed at static state;

[0058] The vehicle speed base speed V1, torque coupling speed V2 and dynamic safety speed V3 are calculated respectively.

[0059] A nonlinear weight distribution mechanism is adopted to selectively weight the vehicle base speed V1, torque coupling speed V2 and dynamic safety speed V3.

[0060] As shown in Table 1, the vehicle speed base speed V1, torque coupling speed V2 and dynamic safety speed V3 are selected for different application scenarios.

[0061] Table 1 Dominant vehicle speed under different working conditions

[0062]

[0063] S4. Based on the vehicle speed base speed V1, the torque coupling speed V2 and the dynamic safety speed V3, a target speed strategy V_target and a speed limit strategy V_ehps are formed.

[0064] V_target=max(V1,V2,V3)×(1-0.2e^(-0.1V));

[0065] V_ehps=min(V_target,N)×SAT(Tm / Tm_limit);

[0066] Among them, SAT is the saturation function, and Tm_limit is the maximum allowable torque of the motor.

[0067] S5. Establish a steering wheel angle dynamic compensation strategy ΔV based on the steering wheel angle Lwis.

[0068] ΔV=k×d(Lwis) / dt×e^(-0.05V), where k is the compensation gain, and d(Lwis) / dt represents the derivative of the steering wheel angle Lwis with respect to time t, that is, the instantaneous rate of change of the steering wheel angle, which is used to reflect how fast the driver turns the steering wheel.

[0069] in,

[0070] When d(Lwis) / dt is large (the steering wheel turns quickly): the control system believes that the driver needs to turn urgently and needs to increase the power response speed;

[0071] When d(Lwis) / dt is small (steering wheel turns slowly): the system maintains smooth power assistance to improve control smoothness.

[0072] The compensation gain k is calibrated through experiments. In the experiment, the vehicle speed is 0 (steering on the spot), 30km / h (low speed), 80km / h (high speed); the steering rate changes in steps: 50deg / s, 100deg / s, 200deg / s, 500deg / s; the load conditions are: no load, half load, full load; experiments are carried out, and the compensation gain k is obtained by evaluating the steering force gradient (N·m / deg), motor response delay (ms), and steering wheel oscillation amplitude (deg).

[0073] Gain sweep by bench test: k = k 初始 ×2^n / 2(n=-4,-2,0,+2,+4).

[0074] Record the system response under different compensation gain k values ​​and select the one that satisfies:

[0075] a. Step response overshoot <15%;

[0076] b. Steady-state error <5%;

[0077] c. Steering force linearity R 2 >0.95.

[0078] According to the calibration results, the following k value range is obtained:

[0079] Vehicle speed (km / h) Recommended k range Physical meaning 0 8～12 High gain and fast response are required for turning on the spot 30 5～8 Balanced flexibility and stability at low speeds 80 2～4 High-speed suppression overcompensation

[0080] S6. Based on the steering wheel angle dynamic compensation strategy, the target speed strategy V_target and the speed limit strategy V_ehps are corrected or compensated.

[0081] S61. According to

[0082] V_target'=V_target+ΔV;

[0083] The target speed strategy V_target is modified to form a new target speed strategy V_target'.

[0084] S62, according to

[0085] ΔVlimit=500·(1-e^-0.02∣d(Lwis) / dt∣)

[0086] The dynamic upper limit compensation ΔVlimit is calculated.

[0087] S63, according to

[0088] Vlimit′=N+ΔVlimit·SAT(Tm / Tm_limit),

[0089] Wherein, N is the standard amplitude of the speed in static state; the speed Vlimit′ upper limit is adjusted.

[0090] When the steering wheel is turned quickly, the speed limit is temporarily allowed to increase (maximum +500rpm) to enhance the power assist capability under sudden working conditions; when static, the standard limit value N is restored.

[0091] The dynamic upper limit compensation ΔVlimit is used to constrain the steering wheel angle dynamic compensation strategy ΔV to prevent the steering wheel angle dynamic compensation strategy ΔV calculation value from abnormally increasing due to noise or algorithm errors. The dynamic upper limit compensation ΔV_limit rigidly limits the steering wheel angle dynamic compensation strategy ΔV to a safe range. The steering wheel angle dynamic compensation strategy ΔV is the "demand signal" of dynamic compensation, which directly affects the correction amplitude of the target speed; ΔV_limit is the "capacity boundary" of dynamic compensation, which constrains the safety range of the final output speed.

[0092] Normal working condition: ΔV is freely adjusted within the ΔV_limit range to optimize dynamic response.

[0093] Extreme working conditions: ΔV_limit is hard-cut to protect system safety. This design ensures the flexibility and reliability of the EHPS system under all working conditions.

[0094] S64, according to

[0095] V_ehps'=min(V_target',Vlimit')×SAT(Tm / Tm_limit),

[0096] The speed limit strategy V_ehps is modified to form a new target speed strategy V_ehps'.

[0097] In the present invention, a speed-dependent control strategy for a new energy vehicle according to the present invention is used for actual road testing. As shown in Table 2, the speed-dependent control strategy is tested in a serpentine test in accordance with ISO-13674-1.

[0098] Table 2 Comparison of data between the original system and the improved system in the ISO-13674-1 serpentine test

[0099]

[0100] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A speed-dependent control strategy for new energy vehicles, characterized in that: The following steps are involved: S1. Collect basic vehicle data, including vehicle speed V, steering wheel angle Lwis, motor real-time torque Tm and driver steering torque Ts; S2, preprocessing vehicle basic data based on S-type function; S3. According to V1=(V_max-V) / V_max×α×N; V2=β×(Ts×Lwis) / (Ts_max×Lwis_max)×N; V3=γ×√(Tm^2+Ts^2) / √2×N / √(Tm_max^2+Ts_max^2); Among them, V1 is the basic speed of the vehicle, V_max is the maximum speed of the vehicle, α∈[0.2,0.6] is the speed attenuation coefficient; V2 is the torque coupling speed, β is the dynamic coupling coefficient, β=tanh(0.01Tm), tanh is the hyperbolic tangent function; V3 is the dynamic safety speed, γ is the safety factor, Tm_max is the maximum motor real-time torque, Ts_max is the maximum driver steering torque, and N is the standard amplitude of the speed at static state; Calculate the vehicle basic speed V1, torque coupling speed V2 and dynamic safety speed V3 respectively; S4, forming a target speed strategy V_target and a speed limit strategy V_ehps based on the vehicle speed base speed V1, the torque coupling speed V2 and the dynamic safety speed V3; S5, establishing a steering wheel angle dynamic compensation strategy ΔV based on the steering wheel angle Lwis; S6. Based on the steering wheel angle dynamic compensation strategy, the target speed strategy V_target and the speed limit strategy V_ehps are corrected or compensated to obtain a new target speed strategy V_target' and a new speed limit strategy V_ehps'.

2. A speed-dependent control strategy for new energy vehicles according to claim 1, characterized in that: The target speed strategy V_target and the speed limit strategy V_ehps are: V_target=max(V1,V2,V3)×(1-0.2e^(-0.1V)); V_ehps=min(V_target,N)×SAT(Tm / Tm_limit); Among them, SAT is the saturation function, Tm_limit is the maximum allowable torque of the motor, and N is the standard amplitude of the speed in static state.

3. A speed-dependent control strategy for new energy vehicles according to claim 1, characterized in that: The dynamic compensation strategy ΔV is ΔV=k×d(Lwis) / dt×e^(-0.05V), where k is the compensation gain, d(Lwis) / dt represents the derivative of the steering wheel angle Lwis with respect to time t, that is, the instantaneous rate of change of the steering wheel angle, which is used to reflect how fast the driver turns the steering wheel.

4. A speed-dependent control strategy for new energy vehicles according to claim 3, characterized in that: The compensation gain 5. A speed-dependent control strategy for new energy vehicles according to claim 3, characterized in that: The target speed strategy V_target and the speed limit strategy V_ehps are corrected based on the steering wheel angle dynamic compensation strategy, including: S61, according to V_target'=V_target+ΔV; Modify the target speed strategy V_target to form a new target speed strategy V_target'; S62, according to ΔVlimit=500·(1-e^-0.02∣d(Lwis) / dt∣) The dynamic upper limit compensation ΔVlimit is calculated; S63, according to Vlimit′=N+ΔVlimit·SAT(Tm / Tm_limit), Wherein, N is the standard amplitude of the speed in static state, and the speed Vlimit′ upper limit is adjusted; S64, according to V_ehps'=min(V_target',V li m i t ′ )×SAT(Tm / Tm_limit), The speed limit strategy V_ehps is modified to form a new target speed strategy V_ehps'.

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