Electric Motor Torque Control for Drivability
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Solution Overview
Problem
Electric vehicles experience a high torque output response relative to accelerator depression, leading to unwanted acceleration sensations at low speeds and compromised acceleration feeling at high accelerator operations.
Innovation Solution
Implementing a control method that adjusts the torque increase rate based on vehicle speed and accelerator operation, using maps to set upper limit values and threshold torques, ensuring a comfortable acceleration feeling by reducing torque increase rate when exceeding thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the torque increase rate is set high to improve acceleration response, then the torque response is improved, but the vehicle may shoot forward against the driver's will at low speeds
Solution Approach 1:
The patent applies dynamics by making the torque increase rate variable rather than fixed. The control unit adjusts the torque increase rate dynamically based on vehicle speed and accelerator operation amount, using different upper limit values at different operating conditions. This resolves the contradiction by allowing high torque response when needed while preventing unwanted acceleration at low speeds through speed-dependent rate limiting.
Solution Approach 2:
The patent changes the parameter of torque increase rate based on operating conditions. By setting different upper limit values for torque increase rate according to vehicle speed and accelerator depression amount, the system optimizes acceleration feeling across different driving scenarios. This parameter adaptation resolves the contradiction between responsive acceleration and controlled low-speed behavior.
2Object-affected harmful factors
If the torque increase rate is set low to prevent shooting forward sensation, then the unwanted acceleration is suppressed, but the acceleration feeling deteriorates
Solution Approach 1:
The system dynamically adjusts the torque increase rate based on real-time operating conditions rather than using a fixed low rate. This allows the system to suppress unwanted acceleration at low speeds while maintaining good acceleration feeling at higher speeds or with larger accelerator operations, resolving the contradiction through conditional rate adjustment.
Solution Approach 2:
The patent changes the torque increase rate parameter according to vehicle speed and accelerator operation amount. By setting higher upper limit values when accelerator operation is large or vehicle speed is higher, the system maintains good acceleration feeling while preventing shooting forward sensation at low speeds with small accelerator operations.
3Device complexity
If a fixed torque increase rate is used, then the control is simple, but the acceleration feeling is compromised across different driving conditions
Solution Approach 1:
The patent implements dynamic adjustment of torque increase rate based on vehicle speed and accelerator operation amount. The control unit selects appropriate upper limit values from predefined sets based on current operating conditions, achieving good acceleration feeling across different driving scenarios while maintaining manageable control complexity through structured lookup tables and conditional logic.
Data Source
Figure 1
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Figure 3A~3C
AI summary
A vehicle driven by an electric motor (136), includes: an accelerator operation amount detection unit (175); a speed detection unit (139); and a control unit (180) configured to calculate a required torque (TRQ) of the electric motor on a basis of a accelerator operation amount and a vehicle speed, calculate a torque increase rate (RATp), which is a required rate at which an effective torque (TAC) for driving the electric motor is increased, on a basis of the required torque, and control the electric motor on a basis of the calculated torque increase rate. The control unit is configured to control the electric motor to operate at a predetermined torque increase rate until the effective torque reaches a predetermined threshold torque (TCHG), and to reduce the torque increase rate below the predetermined torque increase rate after the effective torque reaches the predetermined threshold torque.