Synchronous Motor Torque Control for EV Step-Climbing Lock States
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Solution Overview
Problem
Electric vehicles with synchronous motors can experience overheating when wheels get stuck on a step due to locked motors, leading to restricted output torque and impaired step-climbing ability.
Innovation Solution
An electric vehicle with a synchronous motor directly driving wheels, controlled by a controller that detects a locked state and adjusts torque to a higher search target torque, gradually increasing and decreasing it to prevent overheating and ensure smooth passage over obstacles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the synchronous motor outputs torque in a locked state to enable step-climbing, then the motor can overcome obstacles, but current concentration occurs in a specific phase causing overheating of motor components and wiring
Solution Approach 1:
The patent applies dynamics by switching the motor control strategy based on the locked state detection. When a locked state is detected, the control transitions from normal torque control to a dynamic control mode where torque is increased in small increments with pauses, allowing the system to adapt to changing conditions and prevent overheating while still achieving step-climbing capability.
Solution Approach 2:
The patent implements periodic action by increasing motor torque in discrete steps with pause intervals rather than continuous increase. The controller increases torque by a predetermined amount, pauses for a predetermined time period, then repeats the process if the locked state persists. This periodic approach allows heat dissipation between torque increases, preventing component overheating.
2Reliability
If the output of the synchronous motor is restricted to suppress overheat, then component protection is achieved, but step-climbing ability is impaired
Solution Approach 1:
The patent applies preliminary action by detecting the locked state before significant overheating occurs and implementing torque control adjustments in advance. The controller monitors motor current and detects locked states early, then proactively adjusts torque output to prevent damage while maintaining step-climbing capability. This preliminary detection and response prevents the need for severe output restrictions.
Solution Approach 2:
The patent changes operational parameters dynamically based on the locked state. Instead of restricting output to fixed low levels, the controller adjusts torque as a variable parameter, increasing it in small predetermined increments during locked state operation. This parameter change approach allows the motor to deliver sufficient torque for step-climbing while staying within safe thermal limits through controlled, incremental torque increases.
3Reliability
If additional components like clutches are added to prevent locked state overheating, then component protection is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by using the existing motor control system to detect locked states and adjust torque output without requiring additional mechanical protection components. The controller monitors motor current, detects locked conditions, and autonomously adjusts torque to prevent overheating. This self-service approach eliminates the need for clutches or other mechanical disconnect devices, maintaining system simplicity while achieving reliable overheat protection.
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
Improves run-through performance by preventing overheating and maintaining motor functionality while overcoming obstacles without additional components like clutches, enhancing stability and reliability.
Implementation Method 1
an electric motor that directly drives at least one wheel of the vehicle; the electric motor is a synchronous motor
Implementation Method 2
determine, based on motor torque of the electric motor and a number of revolutions of the electric motor, whether the electric motor is in a locked state
Implementation Method 3
concentration of current is caused in a specific phase (one of the three phases). Consequently, components such as the electric motor, three-phase wiring, and an inverter, notably parts and components corresponding to the specific phase, can become overheated
Data Source
AI summary
An electric vehicle includes a motor and a controller. The controller is configured to; based on determining that the electric motor is in the locked state, set a search target torque greater than a value of torque demanded by a driver, and execute an increase of the motor torque up to the set target torque; upon making a determination that the locked state is ceased, store a value of the target torque at a time of making the determination, and execute a decrease of the target torque; and when a second value of the torque demanded by the driver becomes the value of the target torque or more after the decrease of the target torque, set a second value of the target torque in accordance with the second value of the torque demanded by the driver, and drive the electric motor in accordance with the set target torque.