Electric Vehicle Torque Control for Smooth Shift Rev-Matching
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Solution Overview
Problem
In electric vehicles with transmissions, the rapid increase in motor rotational speed during shift-down operations due to low inertia and low rotational resistance makes rev-matching difficult, as the motor rotational speed tends to exceed intended speeds, requiring delicate accelerator manipulation.
Innovation Solution
A control device that compensates the target output torque using a slowness characteristic to slow down motor rotational speed changes in non-transmission states, simulating the behavior of a virtual rotary member with higher inertia or resistance, allowing easier rev-matching and smoother shift operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the accelerator is operated to be opened during shift-down operation in non-transmission state, then the motor rotational speed increases rapidly to respond to accelerator opening degree, but the motor rotational speed significantly exceeds the intended motor rotational speed making rev-matching difficult
Solution Approach 1:
The control device changes the parameter of target output torque by adding compensation torque when the clutch is disengaged during shift-down operation. This modification to the torque parameter slows the motor rotational speed response to accelerator operations, preventing excessive speed increases and facilitating rev-matching.
Solution Approach 2:
The control device introduces compensation torque as an intermediary element between the accelerator operation and the motor rotational speed response. This compensation torque acts as a mediating force that moderates the direct relationship between accelerator opening degree and motor speed change, enabling better control during rev-matching.
2Adaptability or versatility
If the clutch is disengaged during shift-down operation, then the driving power transmission path is set in non-transmission state, but the motor rotational speed sensitively responds to accelerator opening degree change and rapidly increases
Solution Approach 1:
The control device modifies the target output torque parameter by adding compensation torque specifically when the clutch is disengaged. This parameter change stabilizes the motor rotational speed by reducing its sensitive response to accelerator operations during the non-transmission state, thereby maintaining speed stability while preserving transmission adaptability.
Solution Approach 2:
The control device applies compensation torque in advance to counteract the expected rapid speed increase that would occur during accelerator operations in non-transmission state. This preliminary anti-action prevents the motor rotational speed from deviating excessively, maintaining stability before the problem arises.
3Speed
If the motor rotational speed is allowed to rapidly increase in non-transmission state, then the response to accelerator operation is quick, but the motor rotational speed significantly exceeds the intended speed range
Solution Approach 1:
The control device changes the target output torque parameter by adding compensation torque to slow down the motor rotational speed response. This parameter modification maintains the responsiveness to accelerator operations while improving the precision of motor rotational speed control, preventing the speed from exceeding the intended range during shift-down operations.
Data Source
AI summary
A control device includes a torque setting section for setting a target output torque of an electric motor based on a driving state including an accelerator operation amount; a non-transmission state determiner section for determining whether a driving power transmission path is in a non-transmission state in which driving power is not permitted to be transmitted from the electric motor to a drive wheel or in a transmission state in which the driving power is permitted; and a torque compensation section for compensating the target output torque, when the non-transmission state determiner section determines that the driving power transmission path is in the non-transmission state. The torque compensation section compensates the target output torque by using a slowness characteristic in which a change in the motor rotational speed which occurs with time is slower when in the non-transmission state than when in the transmission state.