Electric Motor Torque Control for EV Body Vibration Reduction
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Solution Overview
Problem
Vibrations and associated noise in the passenger compartment of electric vehicles due to roadway excitation through tire contact with potholes and bumps are not adequately addressed by existing technologies, leading to increased air noise levels.
Innovation Solution
The electric motor is used to generate compensating forces that counteract the forces induced by roadway excitation, minimizing vibrations and noise by adjusting its drive torque based on sensor-determined vibrations at the subframe or vehicle body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the electric motor is used to generate compensating forces to counteract roadway excitation, then vehicle body vibrations and airborne sound are reduced, but the device complexity increases due to additional sensors and control systems
Solution Approach 1:
The electric motor performs dual functions: it drives the vehicle wheels and simultaneously generates compensating forces to counteract roadway excitation. By utilizing the motor's electromagnetic force generation capability for both propulsion and vibration compensation, the system reduces the need for separate active vibration control actuators, thereby managing device complexity while achieving vibration reduction
Solution Approach 2:
The system uses the electric motor's own force generation capability to compensate for vibrations rather than requiring an entirely separate active control system. The motor serves itself by providing both the primary drive function and the secondary vibration compensation function, reducing the need for additional dedicated components
2Measurement precision
If sensors are added to determine vibrations at the subframe or vehicle body, then the precision of vibration measurement improves, but the device complexity and cost increase
Solution Approach 1:
Existing sensors in the electric vehicle (such as those used for stability control, suspension management, or motor control) are repurposed to detect vibrations at the subframe or vehicle body. By making existing sensors serve multiple functions including vibration detection for noise reduction, the system avoids adding dedicated vibration sensors, thereby maintaining measurement precision while limiting increases in device complexity
3Object-affected harmful factors
If the drive torque of the electric motor is continuously adjusted to generate compensating forces, then vibration reduction effectiveness improves, but the energy consumption increases
Solution Approach 1:
The drive torque adjustment for vibration compensation is applied periodically or intermittently based on detected vibration levels rather than continuously. The control system activates compensating torque only when roadway excitation exceeds certain thresholds, allowing the motor to operate in normal drive mode during steady conditions and switch to vibration compensation mode only when needed, thereby reducing overall energy consumption while maintaining effective vibration control
Solution Approach 2:
The compensating torque is applied only to the extent necessary to counteract detected vibrations rather than maintaining constant maximum compensation. The control system modulates the torque adjustment proportionally to the measured vibration amplitude, applying minimal necessary correction during mild excitation and increasing compensation only when required, thus optimizing energy usage while achieving sufficient vibration reduction
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 approach effectively reduces vehicle body vibrations and airborne sound in the passenger compartment by generating opposing forces through the electric motor, thereby minimizing noise and vibration transmission.
Implementation Method 1
The electric motor is configured to introduce forces into supporting parts of the vehicle body or the subframe to counteract forces introduced by the roadway excitation
Implementation Method 2
The vibrating surfaces of the body stimulate the air space in the vehicle interior and lead to increased air noise levels in the passenger compartment
Data Source
AI summary
A method uses the electric motor (4) of an electric vehicle to reduce vibration of the vehicle body (1). The electric motor (4) is supported on the vehicle body (1) or on the subframe (2) of the electric vehicle. The method includes determining a vibration of a subframe (2) or of the vehicle body (1) in the area of force introduction sites where electric motor (4) is supported. The method proceeds by determining a torque required to be generated by the electric motor (4) to introduce a force into the subframe (2) or into the body (1) for counteracting the force caused by the determined oscillation acting on the subframe (2) or the vehicle body (1) and adjusting at least one driving signal of the electric motor (4) such that the required torque is generated based on the change in the drive torque of the electric motor (4).