Dry Clutch Control for Automated Manual Transmission Vehiclesanalyses the control of a part of the powertrain which has a key role in ride comfort during standing-start and gear-shifting manoeuvres. T

This paper illustrates the application of a model-based adaptive friction compensation on a DC motor servomechanism. The dynamic friction model and the control structure studied previously by the authors were used as a basis for this study. The paper first proposes a two-step off-line method to estimate the nominal static and dynamic parameters associated with the model. Then two adaptive globally stable mechanisms are introduced to deal with structured normal forces and temperature variations. Assuming that a nominal friction model is known and that the friction variations can be suitably structured, adaptation is performed on the basis of only one parameter. The paper presents experimental results validating the identification of the dynamic friction model and the adaptive control scheme. These results show that the adaptive loop improves over a fixed compensation scheme and over a PID controller without friction compensation. © 1997 by John Wiley & Sons, Ltd.

This paper presents a new direct adaptive impedance controller for force/position task that includes transition phases from free to constrained motions. This scheme ensures global asymptotic stability without the need for a priori knowledge of environment stiffness. One of the major consequence of this study is that a generalization of the time-varying impedance leads to integral force feedback. Experimental results on a two-degree-of-freedom planar manipulator are reported.

This paper presents two different aspects concerning the control design laws for induction motors: (1) it derives state operating points (steady-state values for currents and fluxes) parameterized in terms of the desired motor torque, defining minimum-energy operation conditions for the electrical motor. (2) It gives a state-space feedback control design methodology based on Lyapunov analysis which renders the minimum-energy operating points invariant. Several controllers are proposed: P-type control, observer-based P-type control, PI-type control and observer-based PI-type control. The PI-structure and the observer-based control are introduced to deal with motor parameter uncertainties, and the absence of flux measurements, respectively. Stability of all these control schemes is studied. Experimental results are also presented.

To establish empirical verification of a stabilizing controller for non-holonomic systems, the authors implement a hybrid control concept on a 2-DOF mobile robot. Practical issues of velocity control are also addressed through a velocity controller which transforms the mobile robot to a new system with linear and angular velocity inputs. Experiments in the physical meaning of different controller components provide insights which result in significant improvements in controller performance.

The purpose of this note is to contribute to the understanding in how to design discontinuous controllers and to underline their intrinsic aspects and their main properties. The paper gives a sequential control construction based on invariant manifolds and presents several control design possibilities.

In this paper we propose a new dynamic model for friction. The model captures most of the friction behavior that has been observed experimentally. This includes the Stribeck effect, hysteresis, spring-like characteristics for stiction, and varying break-away force. Properties of the model that are relevant to control design are investigated by analysis and simulation. New control strategies, including a friction observer, are explored, and stability results are presented. >

This paper presents some preliminary results on asymptotic stabilization of nonholonomic mechanical systems using the Hamiltonian formulation proposed by van der Schaft and Maschke (1994). Our work seeks to establish a general formulation for designing time-varying controllers for some mechanical system described in the generalized coordinates (position and momentum). The paper gives the change of coordinates that transforms the Hamiltonian system to the form needed to apply the center manifold theorem. We also present a worked example for which stability is analyzed

The aim of this study is to design an optimal controller, in the sense of the stored magnetic energy, where, optimal time varying state trajectories are attained. The control problem encompasses the coupling of the electrical (motor) and mechanical systems

This paper investigates the benefits of applying simple PID+nonlinear controller to subsea robot. This control structure has the advantage of only adding a supplementary nonlinear feedback loop to the existing linear PID-regulator and at the same time improving both the transient and stability margins. Several simulations and experiments have been performed on the experimental subsea robot (VORTEX) and have demonstrated the improvements of the PID+nonlinear controller over the simple PID

This paper presents a hybrid controller for the practical stabilization of general n-dimensional nonlinear systems in one-chained form. This controller consists of two parts: 1) a discrete-time part that practically stabilizes a subset of the system states; and 2) a piecewise continuous-time part that steers the remaining state-components to an arbitrarily small neighborhood of zero. One attractive feature of the proposed control approach is that it straightforwardly allows for generalizations in the sense that integrators can be put in cascade with the control inputs without affecting the closed-loop stability properties. This yields smoother control inputs, which makes the hybrid controller particularly useful for some relevant applications like mobile robots

This paper presents experimental results of a robust nonlinear torque controller for induction motors based on the optimization of the power factor of the machine. This type of controller, which has been designed by Canudas de Wit at. el (1992), first derives the optimal operating points (steady-state values for currents and flux) parameterized in terms of the desired motor torque and then stabilized through a static state about the machine optimal operating points. We have implemented the nonlinear PI-observer-based controller. The PI-structure and the observer-based control are introduced to deal with motor parameter uncertainties and the absence of rotor flux measurements, respectively. This controller ensures torque regulation despite uncertainties on the electrical parameters of the machine. The experimental validation was made on a small machine of 1.1 kW.<>

Nonlinear systems without drift having less inputs than states have been shown not to be stabilizable by pure smooth state feedback, [4]. Examples of such systems are mecanical systems with nonholonomic constraints, i.e. mobile robots. carts, multifinger hands, etc. Asymptotic stabilization via time varying controllers have recently been proposed [14], [6], [12]. As indicated by [14], time-varying controllers seems to have the property of rather slow convergence rate, for the example studied in [14]) the time rate is at most 1/t. In this paper an other type of controller is investigated. Piecewise smooth feedback control is proposed as an alternative to the time-varying control. It is shown that convergence rate is improved and. in some examples, it is even exponential.

Control algorithms for mechanical systems (ie. industrial manipulators, robots, etc.) have been extensively studied in the last decade. We present an extension of the work of (Williamson and Canudas de Wit, 1993) to the PID+u/sub NL/ control structure and we demonstrate the advantages of this approach in a simulation example that represents the second-order mechanical systems subject to state disturbances and control input saturation. Firstly we present the general control law and then present the application of these ideas to the case of the PID-control structure.<>

An asymptotically stable scheme for motion control of rigid robots with induction motor drives is presented. The result is established considering a model that includes the electrical and mechanical dynamics of the induction motors, as well as the full rigid body dynamics of the robot manipulator. The design is carried out in three steps. An inner control loop is designed such that the overall system becomes a cascade connection of two nonlinear subsystems, i.e., the motor electrical dynamics are decoupled from the robot variables. The torque required to track the desired joint trajectory is evaluated. A controller is designed to insure that the torques generated by the motors asymptotically track the desired torque

In this paper we propose two new dynamic friction models that include most of the relevant properties that friction has been observed to have (Stribeck effect, hysteresis behavior, spring-like characteristics in stiction and stick-slip regime). Properties of these models that are relevant to control design are studied. In particular we analyse the dissipative properties of the models. New control strategies are investigated and stability results are presented.

This paper presents an exponentially stable controller for a two-degree-of-freedom robot with nonholonomic constraints. Although this system is controllable, it has been shown to be non-stabilizable via smooth state feedback. In [6], a particular class of piecewise continuous controllers is proposed which exponentially stabilizes the robot about the origin. Here, this approach is extended to stabilize about an arbitrary position and orientation, and to follow a path which is composed of a sequence of straight lines and circle segments, i.e. shortest paths of bounded curvature in the plane. The velocity along the path is to be specified to any desired profile, and may for instance pass through or converge to zero.

This paper presents two different aspects concerning the control design laws for induction motors: (1) It derives state operating points (steady-state values for currents and fluxes)parameterized in terms of the desired motor torque, defining minimum energy operation conditions for the electrical motor. (2) It gives a state space feedback control design methodology based on Lyapunov analysis which renders the minimum energy operating points invariant. A PI-type control is here proposed. The PI-structure is introduced to deal with motor parameter uncertainties. Stability of this control schemes is studied.