Wubing B. Qin

Stability and Frequency Response Under Stochastic Communication Delays With Applications to Connected Cruise Control Design

In this paper we investigate connected cruise control in which vehicles rely on ad hoc wireless vehicle-to-vehicle communication to control their longitudinal motion. Intermittencies and packet drops in communication channels are shown to introduce stochastic delays in the feedback loops. Sufficient conditions for almost sure stability of equilibria are derived by analyzing the mean and covariance dynamics. In addition, the concept of

Digital effects and delays in connected vehicles: Linear stability and simulations

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Exact Stability Analysis of Discrete-Time Linear Systems with Stochastic Delays

string stability is proposed to characterize the input–output response in steady state. The stability results are summarized using stability charts in the plane of the control gains and we demonstrate that the stable regimes shrink when the sampling time or the packet drop ratio increases. The mathematical tools developed allow us to design controllers that can achieve plant stability and string stability in connected vehicle systems despite the presence of stochastically varying delays in the control loop.

Optimal Gear Shift Schedule Design for Automated Vehicles: Hybrid System Based Analytical Approach

To improve the ride quality in connected vehicle platoons, information about the motion of the leader can be transmitted using vehicle-to-vehicle (V2V) communication and such information can be incorporated in the controllers of the following vehicle. However, according to the current V2V standards, dedicated short range communication (DSRC) devices transmit information every 100 ms which introduces time delays into the control loops. In this paper we study the effects of these time delays on the dynamics of vehicle platoons subject to digital control and derive conditions for plant stability and string stability. It is shown that when the time delay exceeds a critical value, no gain combination can stabilize the system. Our results have important implications on connected vehicle design.Copyright

Moment-based plant and string stability analysis of connected cruise control with stochastic delays

This paper provides analytical results regarding the stability of linear discrete-time systems with stochastic delays. Necessary and sufficient stability conditions are derived by using the second moment dynamics which can be used to draw stability charts. The results are applied to a simple connected vehicle system where the stability regions are compared to those given by the mean dynamics. Our results reveal some fundamental limitations of connected cruise control which becomes more significant as the packet drop ratio increases.

Hybrid system based analytical approach for optimal gear shifting schedule design

In this paper, we present a systematic design framework for gear shift schedule using hybrid system theory primarily intended for automated vehicles. The longitudinal motion of the vehicle is regulated by a PI controller that determines the required axle torque. The longitudinal dynamics of the vehicle with a gear box is modeled as a hybrid system, and an optimization-based gear shift schedule design is introduced. This guarantees that the propulsion requirements are delivered while minimizing fuel consumption. The resulting dynamics is proven to be stable in the presence of constraints. We apply our framework to heavy-duty vehicle gear shift schedule design and evaluate the performance of the controller using numerical simulations.

Application of Predictor Feedback to Compensate Time Delays in Connected Cruise Control

In this paper we investigate the concept of connected cruise control (CCC) where vehicles rely on ad-hoc wireless vehicle-to-vehicle (V2V) communication to control their longitudinal motion. While V2V communication potentially allows vehicles to build detailed knowledge about the traffic environment, intermittencies and packet drops introduce stochastic delays into the communication channels that make control very challenging. We derive the mean and covariance dynamics for the corresponding stochastic system and analyze the effects of stochastic delays on vehicular strings. We also provide conditions for plant and string stability using the mean and the covariance. Moreover, we demonstrate that how the stable regimes shrink when the sampling time or the packet drop ratio increases. Our results have important implications regarding safety and efficiency of connected vehicle systems.

Stability analysis of connected cruise control with stochastic delays

In this paper, we present a systematic design for gear shifting using a hybrid system approach. The longitudinal motion of the vehicle is regulated by a PI-controller that determines the required axle torque. The gear scheduling problem is modeled as a hybrid system and an optimization-based gear shifting strategy is introduced, which guarantees that the propulsion requirements are delivered while minimizing fuel consumption. The resulting dynamics is proved to be stable theoretically. In a case study, we compare our strategy with a standard approach used in the industry and demonstrate the advantages of our design for class 8 trucks.Copyright

Scalable stability analysis on large connected vehicle systems subject to stochastic communication delays

In this paper, we investigate a vehicular string traveling on a single lane, where vehicles use connected cruise control to regulate their longitudinal motion based on data received from other vehicles via wireless vehicle-to-vehicle communication. Assuming digital controllers, the sample-and-hold units introduce time-periodic time delays in the control loops and the delays increase when data packets are lost. We investigate the effect of packet losses on plant and string stability while varying the control gains and determine the minimum achievable time gap below which stability cannot be achieved. We propose two predictor feedback control strategies that overcome the destabilizing effect of the time delay caused by the sample-and-hold unit and packet losses.