M Maarten Steinbuch

String-Stable CACC Design and Experimental Validation: A Frequency-Domain Approach

The design of a cooperative adaptive cruise-control (CACC) system and its practical validation are presented. Focusing on the feasibility of implementation, a decentralized controller design with a limited communication structure is proposed (in this case, a wireless communication link with the nearest preceding vehicle only). A necessary and sufficient frequency-domain condition for string stability is derived, taking into account heterogeneous traffic, i.e., vehicles with possibly different characteristics. For a velocity-dependent intervehicle spacing policy, it is shown that the wireless communication link enables driving at small intervehicle distances, whereas string stability is guaranteed. For a constant velocity-independent intervehicle spacing, string stability cannot be guaranteed. To validate the theoretical results, experiments are performed with two CACC-equipped vehicles. Implementation of the CACC system, the string-stability characteristics of the practical setup, and experimental results are discussed, indicating the advantages of the design over standard adaptive-cruise-control functionality.

A fast algorithm to computer the H ∞ -norm of a transfer function matrix

Abstract A fast algorithm is presented to compute the H ∞ - norm of a transfer function matrix, based on the relation between the singular values of the transfer function matrix and the eigenvalues of a related Hamiltonian matrix. The norm is computed with guaranteed accuracy. A very simple method to compute a rather close lower bound on the H ∞ - norm is given.

Advanced Motion Control: An Industrial Perspective*

Industrial feedback motion controllers are tuned using manual loopshaping, according to certain design rules. This controller tuning serves as a benchmark for robust control research as applied to optical and magnetic disk drive storage systems. The design and implementation of robust controllers for the focus servo of a compact disk and the tracking servo of a hard disk mechanism is investigated. The design objective is to achieve good track-following performance in the presence of disk disturbances. H∞ robust control is used to systematically include disturbance and specification models in the standard plant framework. The control design iteration is based on disturbance identification, including implementation within the design cycle. The industrial relevance of robust control is discussed and areas for academic research in robust control are indicated, as feedback from industry.

Velocity trajectory optimization in Hybrid Electric trucks

Hybrid Electric Vehicles (HEVs) enable fuel savings by re-using kinetic and potential energy that was recovered and stored in a battery during braking or driving down hill. Besides, the vehicle itself can be seen as a storage device, where kinetic energy can be stored and retrieved by changing the forward velocity. It is beneficial for fuel consumption to optimize the velocity trajectory in two ways; i) to assist the driver in tracking an optimal velocity trajectory (e.g. input to an Adaptive Cruise Controller); ii) to estimate the future power request trajectory which can be used to optimize the hybrid components use. Taking advantage of satellite navigation, together with the vehicles current mass and road load parameters, an optimization problem is formulated, and solved for a driver defined time constraint. Despite tight velocity constraints, this can result in 5% fuel saving compared to a Cruise Controller with constant velocity setpoint. The benefit of velocity trajectory optimization is indicated with experimental results.

Adaptive control of the radical servo system of a compact disc player

The radial servo system of a compact disc player has to cope with large gain variations which are due to disc dependent optical characteristics, tolerances in mechanical and electrical components and nonlinearity in the generation of the position index. In current players this problem has been solved by using an adaptive control scheme based on an injected signal to identify the process gain. This paper discusses the application of the general Self Tuning Regulator (STR) concept to the control problem of the radial servo system. The STR principle depends on parametric identification and control adaptation without additional excitation of the control loop. The concept has been implemented in an experimental arrangement; it gives good control performance and is insensitive to practical perturbations.

Real-time control of tearing modes using a line-of-sight electron cyclotron emission diagnostic

The stability and performance of tokamak plasmas are limited by instabilities such as neoclassical tearing modes. This paper reports on an experimental proof of principle of a feedback control approach for real-time, autonomous suppression and stabilization of tearing modes in a tokamak. The system combines an electron cyclotron emission diagnostic for sensing of the tearing modes in the same sight line with a steerable electron cyclotron resonance heating and current drive (ECRH/ECCD) antenna. A methodology for fast detection of q = m/n = 2/1 tearing modes and retrieval of their location, rotation frequency and phase is presented. Set-points to establish alignment of the ECRH/ECCD deposition location with the centre of the tearing mode are generated in real time and forwarded in closed loop to the steerable launcher and as a modulation pulse train to the gyrotron. Experimental results demonstrate the capability of the control system to track externally perturbed tearing modes in real time.

μ-synthesis for a compact disc player

SUMMARY This paper considers the design and implementation of robust multivariable controllers for a compact disc mechanism.The design objective is to achieve good track-following and focusing performance in the presence of track disturbances, external mechanical shocks and structured norm-bounded plant uncertainty. This robust performance problem has been solved in the k-framework using the DK-iteration scheme. Limits of implementation necessitate the use of sophisticated model reduction techniques and the use of two parallel digital signal processors. ( 1998 John Wiley & Sons, Ltd.

Robustness Analysis for Real and Complex Perturbations applied to an Electro-Mechanical System

The investigation of closed-loop systems subject to model perturbations is an important issue in order to assure robustness of a control design. A large variety of model perturbations can be described by norm-bounded uncertainty models. In this paper a general approach for modeling structured complex and real-valued parametric perturbations is presented. The resulting robustness analysis problem is solved non-conservatively using real and complex structured singular value calculations. The uncertainty modeling and the robustness analysis are shown for a high-accuracy 5D electro-mechanical positioning device.

Nonlinear stabilization of slip in a continuously variable transmission

One way to predict and control the output torque of a geared neutral CVT is to use the relationship between slip in the variator and transmitted belt torque. This relationship is often referred to as the traction curve. For small slip values, the output torque increases almost linearly with slip. However, at approximately 2% slip, the maximum output torque is reached. For larger slip values, the output torque shows even a decline. Hence, measuring the traction curve in open loop is not possible. Stability analysis shows that by modifying the plant with a nonlinear feedback control torque depending on the slip, a stable closed loop plant with two new defined inputs is obtained. An open loop input torque at this plant now uniquely defines the slip in the system. The primary shaft angular velocity is controlled using a robust stabilizing controller. This controller is tuned using measured frequency response functions at different slip values.

Multivariable control of a compact disc player using DSPs

This paper considers robust multivariable control of a compact disc mechanism using digital signal processors. The design problem is to achieve good track-following and focusing performance in the presence of disturbances and norm-bounded structured plant uncertainty. This robust performance problem has been solved in the /spl mu/-framework using the D-K-iteration scheme. After controller order reduction, the /spl mu/-based controller has been implemented using two parallel digital signal processors.