Autonomous Vehicle Steering Control via Dynamic Mass Center Calculation
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Solution Overview
Problem
Conventional steering control systems for autonomous driving vehicles often result in understeering, particularly at the beginning of turns, due to using the rear axle as a control reference, leading to discomfort for passengers and inefficient navigation.
Innovation Solution
Dynamically determining the vehicle mass and mass center of the autonomous driving vehicle, using segment masses and their respective locations, to generate precise steering and speed control commands, thereby reducing understeering and passenger discomfort during turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rear axle is used as a control reference for steering, then the control system can align the reference to the planned route, but the front portion of the vehicle experiences understeering and drifts off the planned route
Solution Approach 1:
The vehicle is divided into multiple segments (front portion, rear portion, etc.) with each segment having its own mass and center of mass. The control system calculates the overall center of mass by combining these segment centers, enabling more accurate steering control that accounts for the distributed mass of different vehicle portions rather than treating the vehicle as a single rigid body referenced to the rear axle.
Solution Approach 2:
The control reference is shifted from a one-dimensional rear axle location to a two-dimensional center of mass location that can be positioned anywhere within the vehicle footprint based on mass distribution. This dimensional shift allows the control system to account for both longitudinal and lateral mass distribution, improving steering accuracy.
2Ease of operation
If steering control is based on the rear axle position, then the control system can determine steering commands, but the front portion of the vehicle turns delayed and requires overcorrection
Solution Approach 1:
The control system pre-calculates the center of mass position based on segment masses and their locations before executing steering commands. This preliminary determination of the accurate control reference point allows the system to issue steering commands that account for the vehicle's actual mass distribution, preventing delayed turning response and reducing the need for overcorrection.
3Device complexity
If the rear axle is used as the control reference, then the GPS sensor location is simplified, but passengers sitting upfront feel uncomfortable during turns
Solution Approach 1:
The center of mass calculation acts as an intermediary between the simple rear axle GPS reference and the complex reality of vehicle dynamics. By introducing this calculated center of mass point that incorporates segment mass distribution, the system maintains the simplicity of using a single reference point while eliminating the harmful effect of passenger discomfort through more accurate steering control.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
In one embodiment, a request is received to turn the autonomous driving vehicle (ADV) from a first direction to a second direction. In response to the request, a number of segment masses of a number of segments of the ADV are determined. The segment masses are located on a plurality of predetermined locations within a vehicle platform of the ADV. A location of a mass center for an entire ADV is calculated based on the segment masses of the segments of the ADV, where the mass center represents a center of an entire mass of the entire ADV. A steering control command based on the location of the mass center of the entire ADV for steering control of the ADV.