Design of a pressure modulator using fast-acting bistable valves

Fast-acting pneumatic valves, combined with a slip-control braking algorithm, have recently been used to improve the straight-line braking performance of an experimental heavy goods vehicle, on low friction roads, by 16%. This paper describes how the fast-acting valves, which were central to the aforementioned research, were designed for use on a commercial vehicle. Design equations, as well as a generalized design method, are first presented for the fast-acting bistable pneumatic valve. A pressure observer is developed to predict the brake chamber pressure in cases where a pressure transducer is mounted upstream. A simple fault detection algorithm is then introduced, which utilizes some of the calculations made in the pressure observer, and is shown to correctly identify faults on a real vehicle. Performance comparisons are made between the new modulator and a conventional heavy goods vehicle electro-pneumatic brake system. Closed-loop frequency response tests show that the control bandwidth of brake chamber pressure on a heavy goods vehicle can be increased from 1.5 Hz to 10 Hz using the new hardware.

Nonlinear observer-based exhaust manifold pressure estimation and fault detection for gasoline engines with exhaust gas recirculation

This article presents a nonlinear observer-based method to estimate the exhaust manifold pressure for the gasoline engines equipped with an exhaust gas recirculation system. A dynamic model is designed to estimate the exhaust manifold pressure, which includes both the intake manifold and exhaust manifold dynamics focusing on gas mass flows. Based on the developed model, a nonlinear exhaust manifold pressure observer is proposed to replace the exhaust manifold pressure sensor, and the global convergence is analyzed by a constructed Lyapunov function and the physical meaning of the time-varying parameters. The experimental validations show that the observer-based exhaust manifold pressure estimator is able to converge to the real value at arbitrary initial value and estimates the exhaust manifold pressure accurately during both the steady-state and transient conditions. Finally, the proposed exhaust manifold pressure observer is applied into the fault detection problem for the exhaust gas recirculation system. The experimental validations show that the observer is able to be used to estimate the exhaust gas recirculation ratio and as an extra signal to assist to detect the faults of the exhaust gas recirculation system accurately.

Pressure Observer Based Adaptive Dynamic Surface Control of Pneumatic Actuator with Long Transmission Lines

In this paper, the needle insertion motion control of a magnetic resonance imaging (MRI) compatible robot, which is actuated by a pneumatic cylinder with long transmission lines, is considered and a pressure observer based adaptive dynamic surface controller is proposed. The long transmission line is assumed to be an intermediate chamber connected between the control valve and the actuator in series, and a nonlinear first order system model is constructed to characterize the pressure losses and time delay brought by it. Due to the fact that MRI-compatible pressure sensors are not commercially available, a globally stable pressure observer is employed to estimate the chamber pressure. Based on the model of the long transmission line and the pressure observer, an adaptive dynamic surface controller is further designed by using the dynamic surface control technique. Compared to the traditional backstepping design method, the proposed controller can avoid the problem of “explosion of complexity” since the repeated differentiation of virtual controls is no longer required. The stability of the closed-loop system is analytically proven by employing the Lyapunov theory. Extensive experimental results are presented to demonstrate the effectiveness and the performance robustness of the proposed controller.