Research Article Sliding Mode Control for Active Suspension System with Data Acquisition Delay Uiliam Nelson L. T. Alves, José Paulo F. Garcia, Marcelo C. M. Teixeira, Saulo C. Garcia, and Fernando B. Rodrigues Control Research Laboratory, Department of Electrical Engineering, Univ Estadual Paulista (UNESP), Carlos Rossi, Avenue No. 1370, 15385-000 Ilha Solteira, SP, Brazil Correspondence should be addressed to Uiliam Nelson L. T. Alves; uiliamlendzionalves@gmail.com Received 29 October 2013; Revised 7 February 2014; Accepted 12 February 2014; Published 9 April 2014 Academic Editor: Dan Wang Copyright © 2014 Uiliam Nelson L. T. Alves et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. his paper addresses the problem of control of an active suspension system accomplished using a computer. Delay in the states due to the acquisition and transmission of data from sensors to the controller is taken into account. he proposed control strategy uses state predictors along with sliding mode control technique. Two approaches are made: a continuous-time and a discrete-time control. he proposed designs, continuous-time and discrete-time, are applied to the active suspension module simulator from Quanser. Results from computer simulations and experimental tests are analyzed to show the efectiveness of the proposed control strategy. 1. Introduction here are diferent approaches to control active suspension systems:  ∞ control [1, 2], proportional integral sliding mode control [3, 4], linear quadratic regulator [5], fuzzy controllers [6], artiicial neural networks [7], and so forth. In this paper focus is given to problems that can arise when computers do the control. In this context, the sampling time involved in the process and possible delays sampled signals may damage the control performance. hese signal delays can arise in Networked Control Systems (NCS) where the communication between the elements of the control loop is done by a nonideal shared digital network [8, 9]. Wireless Networked Control Systems (WNCS) usually show delays of many sampling periods and cannot be ignored [10]. he main advantage of Variable Structure Control with Sliding Mode (VSC/SM) is its robustness with respect to matched uncertainties, representing disturbances in control input, and parametric uncertainties or even system modeling uncertainties, provided that they belong to the image of the control input matrix [11, 12]. When the control signal is generated by microprocessors, besides sampling time, the system performance is greatly compromised when delays in both data acquisition and data transmission occur. In VSC/SM, this issue is even more important. By using a high speed switching control law in order to take the states trajectory to a sliding surface dependent on the current states, if the states used are delayed, the control law may not direct the states to this surface, which can also generate performance loss or even lead system to instability [13, 14]. he damage caused by delays to sliding mode control motivates several studies [15–18]. his paper proposes a strategy that uses state predictors along with VSC/SM in order to perform control of an active suspension system in presence of input control distur- bance and data acquisition delay of many sampling periods. With purpose of comparison, it proposes two designs: one continuous-time control and one discrete-time control. In both cases, the control signal is generated from a digital computer. Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2014, Article ID 529293, 13 pages http://dx.doi.org/10.1155/2014/529293