Vehicle Drivetrain Simulator Stiffness Compensation
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Solution Overview
Problem
Testing of self-driving vehicles on simulation equipment differs from real-road conditions due to altered stiffness and damping properties, leading to unwanted oscillations and inaccuracies in velocity control.
Innovation Solution
A compensation control signal is applied to counteract the effects of stiffness and damping differences by determining and adjusting for changes in vehicle components when mounted to a test apparatus, using a combination of load and mass compensation factors to simulate real-road conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle is mounted to the test apparatus for simulating driving conditions, then the vehicle can be tested in controlled conditions, but the stiffness and damping properties are altered causing unwanted oscillations and inaccuracies in velocity control
Solution Approach 1:
The patent modifies the dynamic parameters of the test apparatus by actively adjusting the stiffness and damping characteristics of the coupling between the test motors and the vehicle drivetrain. This is achieved through control signals that adjust the mechanical impedance of the coupling mechanism, allowing the system to maintain accurate velocity control while accounting for the altered physical properties during mounting.
2Ease of operation
If the vehicle is mounted to the test apparatus, then controlled testing can be performed, but velocity control accuracy deteriorates due to stiffness and damping differences
Solution Approach 1:
The patent implements a feedback control mechanism where the actual velocity of the vehicle is continuously measured and compared to the commanded velocity. The controller then generates compensation signals that adjust the test motor outputs based on the velocity error, thereby maintaining accurate velocity control despite the stiffness and damping alterations caused by mounting the vehicle to the test apparatus.
3Measurement precision
If compensation control signals are applied to counteract stiffness and damping differences, then velocity control accuracy is improved, but the control system complexity increases
Solution Approach 1:
The patent introduces a controller as an intermediary element between the test motors and the vehicle drivetrain. This controller acts as a mediator that processes velocity commands, measures actual velocity, calculates compensation signals based on the velocity error and known stiffness/damping characteristics, and adjusts the motor outputs accordingly. This intermediary layer manages the complexity by centralizing the compensation logic in a dedicated control unit.
Data Source
AI summary
Aspects of the invention relate to a method comprising: determining an output torque at a wheel of a vehicle mounted to a test apparatus comprising an external motor, the output torque being in response to a command; determining a correction factor based on the output torque and at least one coefficient associated with a reaction of a component of the vehicle and/or of the test apparatus to an applied torque at the vehicle; and controlling the external motor to apply the correction factor to the wheel of the vehicle.