The Effects of Powertrain Mechanical Response on the Dynamics and String Stability of a Platoon of Adaptive Cruise Control Vehicles

TL;DR

This paper analyzes how the mechanical response of vehicle powertrains affects the dynamics and stability of vehicle platoons with adaptive cruise control, revealing new effects of acceleration feedback and proposing a frequency-dependent gain to improve performance.

Contribution

It introduces the effects of acceleration-feedback control on platoon stability and proposes a frequency-dependent gain to mitigate oscillations while maintaining disturbance reduction.

Findings

Disturbance reduction is faster with small feedback gain for marginal stability.

Asymptotic disturbance magnitude decreases as erf(ct/√n) with increasing vehicle number.

A frequency-dependent gain can eliminate oscillations without compromising disturbance attenuation.

Abstract

The dynamics of a platoon of adaptive cruise control vehicles is analyzed for a general mechanical response of the vehicle's power-train. Effects of acceleration-feedback control that were not previously studied are found. For small acceleration-feedback gain, which produces marginally string-stable behavior, the reduction of a disturbance (with increasing car number n) is found to be faster than for the maximum allowable gain. The asymptotic magnitude of a disturbance is shown to fall off as erf(ct./sq. rt. n) when n goes to infinity. For gain approaching the lower limit of stability, oscillations in acceleration associated with a secondary maximum in the transfer function (as a function of frequency) can occur. A frequency-dependent gain that reduces the secondary maximum, but does not affect the transfer function near zero frequency, is proposed. Performance is thereby improved by elimination of the undesirable oscillations while the rapid disturbance reduction is retained.