Rotary Electric Machine Torque Control for Upshift Drivability
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Solution Overview
Problem
In electromotive vehicles, upshifts can lead to changes in decelerating force due to limited input electric power, causing drivability issues as existing control systems struggle to maintain consistent braking force.
Innovation Solution
An electronic control unit is implemented to manage the rotary electric machine's torque, gradually increasing it during upshifts when input electric power is limited, allowing the decelerating force to transition smoothly into decelerating force, and controlling torque output to minimize changes in decelerating force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotation speed of the motor generator is decreased by upshifting to prevent exceeding the upper limit value, then the durability of the motor generator is improved, but the decelerating force of the vehicle changes, deteriorating drivability
Solution Approach 1:
The electronic control unit performs preliminary action by gradually increasing the negative torque of the motor generator before the upshift occurs. This advance preparation ensures that when the upshift happens and decelerating force naturally decreases, the pre-applied negative torque compensates for this reduction, maintaining consistent overall decelerating force and preserving drivability while still allowing the upshift to protect motor generator durability
Solution Approach 2:
The system changes the torque parameter of the motor generator dynamically in response to upshift conditions. By adjusting the negative torque level based on detected upshift events and battery charge capacity, the system compensates for decelerating force changes caused by upshifts, resolving the contradiction between protecting motor generator durability and maintaining drivability
2Ease of operation
If negative torque is increased to compensate for decelerating force reduction during upshift, then drivability is improved, but the input electric power required exceeds the battery's upper limit value
Solution Approach 1:
The system applies partial action by providing only the necessary amount of negative torque to compensate for decelerating force reduction, not exceeding what the battery can supply. The electronic control unit calculates the appropriate torque level based on battery charge capacity, applying just enough compensation to maintain drivability without demanding excessive input electric power that would exceed the upper limit value
Solution Approach 2:
The electronic control unit continuously monitors battery charge capacity and adjusts the negative torque output accordingly. This feedback mechanism ensures that the torque compensation remains within the battery's input electric power limits while still effectively maintaining drivability during upshift events
3Speed
If the speed ratio of the transmission device is increased by upshifting, then the rotation speed of the input shaft is reduced, but the decelerating force changes, affecting vehicle performance
Solution Approach 1:
The system applies a counterbalancing force through negative torque from the motor generator to offset the reduction in decelerating force caused by upshifting. When the transmission ratio increases and naturally reduces decelerating force, the pre-applied negative torque acts as a counterweight, compensating for this loss and maintaining overall decelerating force consistency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces the deterioration of drivability by gently changing decelerating force during upshifts, ensuring a smoother driving experience even with limited electric power.
Implementation Method 1
a rotary electric machine serving as a drive source of a vehicle and a generating source for generating electric power
Implementation Method 2
when decelerating force acts on the vehicle due to engine brake force of the engine
Data Source
AI summary
An electromotive vehicle includes: an electrical storage device; a rotary electric machine; a transmission device; an engine; and an electronic control unit. The electronic control unit is configured to, when decelerating force acts on the vehicle due to engine brake force of the engine and upshift control is executed in the transmission device and when an upper limit value of input electric power that is allowed at the time of charging the electrical storage device is smaller than a threshold, control the rotary electric machine such that torque of the rotary electric machine gradually increases by the time the upshift control completes, at which the decelerating force that acts on the vehicle becomes decelerating force reduced as a result of the upshift control.