Vehicle Propulsion Motor Torque Modulation for Rough-Road Traction
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Solution Overview
Problem
Conventional vehicle propulsion motors aim for smooth torque output without ripple, but this approach may not be desirable in all conditions, particularly for improved traction on rough roads.
Innovation Solution
A method for modulating torque output using cyclic currents with evenly spaced phase differences and applying pulse-width modulated voltage pulses to generate a torque fluctuation similar to that of an internal-combustion engine, achieved by adding phase shifts or amplitude modulations to the applied currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current control using inverter circuits is used to achieve smooth torque output without ripple, then ride comfort is improved, but traction performance on rough roads deteriorates
Solution Approach 1:
The patent implements dynamic torque control by enabling two distinct torque output modes: a first torque mode with suppressed ripple for smooth operation, and a second torque mode with intentional ripple for improved traction. The system dynamically switches between these modes based on driving conditions, allowing the torque characteristics to adapt rather than remain static. This resolves the contradiction by making the torque output flexible rather than fixed.
Solution Approach 2:
The patent changes the torque output parameter by controlling the inverter to produce different current waveforms. In the first mode, sinusoidal currents are used to minimize torque ripple. In the second mode, the currents are modified to generate torque ripple that mimics internal combustion engine characteristics. This parameter change allows the system to optimize for either comfort or traction depending on the selected mode.
2Ease of operation
If torque ripple is eliminated to provide smoother operation, then ride comfort is improved, but recovery of traction on rough roads is hindered
Solution Approach 1:
The system provides dynamic adaptability by allowing switching between smooth torque operation and torque-ripple operation. When traction recovery is needed on rough terrain, the system transitions to the second torque mode that generates appropriate ripple characteristics, thereby adapting to the changing environmental conditions rather than maintaining a single fixed operation mode.
Solution Approach 2:
The electric motor system is designed to perform multiple functions: it can operate in a smooth torque mode for normal driving conditions and in a torque-ripple mode for traction recovery scenarios. This multi-functionality allows a single system to serve both comfort-oriented and performance-oriented purposes, eliminating the need for separate systems for different operating conditions.
3Reliability
If fluctuating torque similar to internal-combustion engine is generated, then traction on rough roads is improved, but driver comfort may be reduced
Solution Approach 1:
The system dynamically adapts torque characteristics to match driver expectations and road conditions. During normal operation, smooth torque is provided for comfort. When traction is needed, fluctuating torque is generated but only temporarily and selectively, allowing the system to balance comfort and performance based on real-time requirements rather than continuously compromising either.
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
The modulated torque provides improved traction on rough roads without causing driver discomfort, mimicking the fluctuating torque of internal-combustion engines and allowing for selectable torque modes.
Implementation Method 1
a motor for propelling a vehicle utilizes a permanent magnet synchronous motor with a rotor that has permanent magnets and a stator that has coils. The motor may be free of commutators and generate currents that are synchronous to a rotating magnetic field provided by the rotor. The currents may be applied to the coils and may cause the motor to generate torque.
Data Source
AI summary
A method for modulating torque of a vehicle propulsion motor driven by first, second and third cyclic currents mutually shifted by electrical angles of 120 degrees and applied in accordance with a rotating magnetic field by a rotor is provided with: applying pulse-width modulated voltage pulses respectively to switching devices to generate the first, second and third cyclic currents; and adding a phase shift to the first, second and third cyclic currents relative to the rotating magnetic field, or causing an amplitude modulation in the first, second and third cyclic currents.