Slip Control Device Dead Time Compensation
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Solution Overview
Problem
Conventional slip control devices for electric vehicles face challenges in maintaining stable and accurate slip control due to long dead times in communication and calculation delays, which can lead to deteriorated controllability, especially when responding to driver inputs and road surface disturbances.
Innovation Solution
A slip control device that includes an allowable rotation speed calculator, a PI/PID controller, an adder, and a dead time compensator using the Smith method, which generates a torque compensation value by excluding integral compensation and using proportional and differential compensations to stabilize wheel rotation speed, thereby improving control accuracy and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional PID control is used for slip control, then the control structure is simple, but the controllability deteriorates when dead time becomes long
Solution Approach 1:
The Smith predictor performs preliminary prediction of the future wheel rotation speed by using the control target model and current control input. This predicted future speed is then used for control calculation, effectively compensating for the dead time delay without requiring complex controller redesign. The prediction is made in advance of the actual measurement becoming available.
2Speed
If the Smith method is used to compensate for dead time, then the response to target input is satisfactory, but the response to disturbance deteriorates
Solution Approach 1:
The invention introduces a disturbance observer that continuously monitors the actual wheel rotation speed and compares it with the predicted speed from the Smith predictor. When a disturbance is detected (difference between actual and predicted speed), the disturbance observer calculates the disturbance torque and feeds it back to the control input, enabling real-time compensation for road surface reactions and other disturbances.
3Reliability
If an additional compensator is introduced to improve disturbance response, then the disturbance response improves, but control designing becomes more complex and requires more man-hours
Solution Approach 1:
The invention merges the Smith predictor for dead time compensation and the disturbance observer for disturbance rejection into a single integrated control device. The control target model is shared between both functions, and the control input is jointly optimized to achieve both target tracking and disturbance rejection, eliminating the need for separate compensators and reducing design complexity.
Data Source
Figure 1
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Figure 3(a)~3(b)
AI summary
The present invention includes: a PI/PID controller (13) that generates a torque compensation value KPID through PI control or PID control, from a deviation between an allowable rotation speed and a rotation speed of a wheel; an adder (16) that adds the torque compensation value to a torque command input value received from a higher-order controller (3), thereby obtaining a torque command output value; and a dead time compensator (17) that has a control target model (18) including a dead time and that applies a dead time compensation in generation of the torque compensation value by the Smith method. An input to the dead time compensator (17) is an output of a P compensation or a PD compensation excluding an I compensation from a PI compensation or a PID compensation.