EV Regenerative Braking Control for Precise Following Stops
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Solution Overview
Problem
Existing control methods for electric vehicles do not adequately consider the presence of a preceding vehicle, which can lead to the host vehicle getting too close to the preceding vehicle during deceleration or stoppage, especially when the preceding vehicle has a larger deceleration rate.
Innovation Solution
A control method for electric vehicles that involves estimating disturbance torque, calculating torque command values based on accelerator operation and angular velocity, and adjusting braking and driving forces to converge the torque command value to the disturbance torque, while also setting a target stop position and calculating a second torque command value to ensure smooth stopping at the intended position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the host vehicle decelerates by regenerative braking force of the motor without considering the preceding vehicle's state, then the vehicle can be stopped even on a sloped road by converging the torque generated by the motor to the estimated disturbance torque, but the host vehicle may get too close to the preceding vehicle when the preceding vehicle has a larger deceleration than the host vehicle
Solution Approach 1:
The control device calculates a second torque command value based on the difference between the target angular velocity (calculated from distance to target stop position) and the actual angular velocity of the motor. This feedback mechanism continuously adjusts the torque command to ensure the vehicle stops at the appropriate position while considering the preceding vehicle's state, thereby resolving the contradiction between stopping reliability on sloped roads and avoiding getting too close to the preceding vehicle.
Solution Approach 2:
The system dynamically adjusts the torque command value by combining the first torque command value (based on accelerator operation amount) with the second torque command value (based on distance to target stop position). This dynamic adjustment allows the vehicle to adapt its deceleration profile in real-time according to the preceding vehicle's state, ensuring both reliable stopping on sloped roads and appropriate spacing from the preceding vehicle.
2Ease of operation
If the torque command value is converged to the disturbance torque without considering target stop position, then the motor torque can be controlled to match disturbance torque for smooth stopping, but the vehicle cannot stop at an appropriate position when a preceding vehicle exists
Solution Approach 1:
The control device merges two torque command values: the first torque command value (for smooth deceleration based on accelerator operation) and the second torque command value (for precise stop position control based on distance to target stop position). By combining these two control objectives, the system achieves both smooth stopping and accurate stopping position control, resolving the contradiction between ease of operation and stopping position accuracy.
Solution Approach 2:
The system changes the torque command parameter dynamically by adjusting it based on the difference between target angular velocity and actual angular velocity. This parameter adjustment ensures that the motor torque not only converges to the disturbance torque for smooth stopping but also achieves the target stop position accurately, even when a preceding vehicle is present.
Data Source
AI summary
A control method for an electric vehicle using a motor as a traveling drive source to decelerate by a regenerative braking force of the motor, including: obtaining an accelerator operation amount; estimating a disturbance torque acting on a vehicle body of the electric vehicle; obtaining an angular velocity of a rotating body that correlates to a rotation speed of a drive shaft which drives the electric vehicle; calculating a first torque command value based on the accelerator operation amount; setting the first torque command value to a torque command value; controlling a torque generated in the motor based on the torque command value; setting a target stop position at the time of stopping the electric vehicle; calculating a target angular velocity of the rotating body according to a distance from the electric vehicle to the target stop position; calculating a second torque command value for stopping the electric vehicle at the target stop position based on a difference between the target angular velocity and the obtained angular velocity; and converging the torque command value to the disturbance torque by setting the second torque command value to the torque command value and adjusting the braking and driving forces of the motor according to a distance to the target stop position, when the accelerator operation amount decreases or becomes zero and the electric vehicle is about to stop.