One-Pedal Speed Control for Off-Road Electric Vehicles
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Solution Overview
Problem
Conventional vehicles require two-foot driving techniques for precise control of wheel speeds during off-road driving, which can be challenging for novice drivers, and electric all-wheel drive vehicles lack a straightforward method to control wheel speeds using a single pedal.
Innovation Solution
A vehicle system with independent electric machines at each axle, controlled by a controller that maps accelerator pedal positions to target wheel speeds and adjusts torque to maintain driver-demanded speeds, enabling one-pedal driving mode by using closed-loop feedback control to track target electric machine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional two-foot driving techniques are used for precise wheel speed control, then control precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system enables one-pedal driving mode where the accelerator pedal alone controls both acceleration and deceleration. The controller automatically manages torque delivery and regenerative braking based on pedal position, eliminating the need for drivers to coordinate both accelerator and brake pedals. The vehicle system serves itself by automatically adjusting torque distribution across axles and wheels based on detected pedal position and wheel speed feedback.
2Ease of operation
If one-pedal driving mode is implemented, then ease of operation is improved, but control precision deteriorates
Solution Approach 1:
The system employs closed-loop feedback control where wheel speed sensors continuously monitor actual wheel speeds and feed this information back to the controller. The controller compares measured wheel speeds with target speeds derived from accelerator pedal position, then adjusts torque commands to electric machines to eliminate speed errors. This feedback mechanism maintains precise wheel speed control despite the simplified one-pedal interface.
Solution Approach 2:
The system dynamically adjusts torque distribution across different axles and wheels based on real-time conditions. The controller modifies torque commands to electric machines according to pedal position, wheel speed feedback, and vehicle operating conditions. This dynamic torque management enables precise speed control while maintaining the simplicity of one-pedal operation.
3Measurement precision
If torque is commanded based on speed error, then speed control accuracy is improved, but device complexity increases
Solution Approach 1:
The controller performs multiple functions using a single integrated control system. It maps accelerator pedal positions to target wheel speeds, calculates speed errors, determines torque commands, and distributes torque across multiple electric machines and axles. The same controller handles both speed control and torque management, eliminating the need for separate control systems and reducing overall device complexity despite the sophisticated control algorithm.
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
Enables precise control of wheel speeds and vehicle propulsion using a single pedal, simplifying off-road driving by automatically adjusting torque to maintain desired speeds regardless of terrain or grade, reducing the need for two-foot driving techniques.
Implementation Method 1
an electric machine configured to power wheels
Implementation Method 2
command a positive torque to the first electric machine based an error between the target electric machine speed and a measured speed
Data Source
AI summary
A vehicle with one-pedal driving mode includes a first axle having a first electric machine configured to power first wheels and a second axle having a second electric machine configured to power second wheels. A controller is programmed to, in response to a request for one-pedal driving mode, map pedal positions of the accelerator pedal to speeds of the first and second wheels such that each of the pedal positions corresponds to a driver-demanded speed of the first and second wheels, and control one or more of the electric machine so that the vehicle is propelled according to the driver-demanded speed.