CVT Regenerative Speed Control Undershoot Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional vehicle regenerative speed control devices experience undershooting, where the actual transmission input rotational speed falls below the lower-limit rotational speed when decreasing the transmission input rotational speed based on a request for a decrease in regeneration amount, due to delayed follow-up response in feedback transmission control.
Innovation Solution
A controller is implemented to perform regenerative speed control by downshifting the continuously variable transmission to the low gear ratio side, increasing the rotational speed of the transmission input shaft, and controlling the rotational speed decrease change rate to be lower than the increase change rate, ensuring the transmission input rotational speed reaches the lower-limit rotational speed with a large angle intersection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback transmission control is carried out with lower-limit rotational speed set as target rotational speed, then the control system can maintain necessary hydraulic pressure, but the follow-up response of actual transmission input rotational speed is delayed
Solution Approach 1:
The system performs preliminary action by setting a rotational speed command value that is higher than the lower-limit rotational speed before the actual speed reaches it. This anticipatory control compensates for the expected delay in follow-up response, ensuring the actual speed will not fall below the lower limit even with delayed response.
Solution Approach 2:
The controller applies preliminary anti-action by preemptively increasing the rotational speed command value above the lower-limit threshold. This counteracts the anticipated undershooting effect caused by delayed feedback response, preventing the actual speed from dropping below the critical lower limit.
2Speed
If upshifting is carried out to decrease transmission input rotational speed, then the rotational speed decreases with good response, but the rotational speed decrease change rate is increased causing undershooting
Solution Approach 1:
The system applies dynamics by making the rotational speed command value dynamically adjustable based on operational conditions. The command value is set higher than the lower-limit rotational speed during deceleration with regeneration request, creating a dynamic buffer zone that prevents undershooting while allowing rapid speed adjustment.
Solution Approach 2:
The controller changes the parameter of rotational speed command value to be variable rather than fixed at the lower limit. By setting the command value higher than the lower-limit rotational speed, the system creates a margin that accommodates the high decrease rate from upshifting without causing the actual speed to fall below the limit.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a vehicle regenerative speed control device for suppressing undershooting, in which the actual transmission input rotational speed falls below a lower-limit rotational speed, when decreasing the transmission input rotational speed based on a request for a decrease in the regeneration amount during regenerative speed control. The present invention has a belt-type continuously variable transmission (6), a motor generator (4), and a main oil pump (14). The FF hybrid vehicle has a hybrid control module (81) which, when there is a request for an increase in the regeneration amount while decelerating, performs a regenerative speed control for downshifting the belt-type continuously variable transmission (6) to the low gear ratio side, and increasing rotational speed of a transmission input shaft to which the motor generator (4) is connected. The hybrid control module (81) also performs a control for making the rotational speed decrease change rate of the Pri end command rotational speed lower than the rotational speed increase change rate of the Pri end command rotational speed, when the Pri end command rotational speed is being decreased based on a request for a decrease in the regeneration amount during regenerative speed control.