Showing papers by "Masayoshi Tomizuka published in 2001"

Contouring control of machine tool feed drive systems: a task coordinate frame approach

Abstract: We show that contouring performance can be viewed as a regulation problem in a moving task coordinate frame that is attached to the desired contour. By transforming the machine tool feed drive dynamics to this task coordinate frame, a control law is designed to assign different dynamics to the tangential and normal directions. The transformation also illustrated the effect of contour curvature and feed rate in the control action as well as the system dynamics in the task coordinate frame. The resulting control law consists of a linear time-varying proportional-plus-derivative (PD) position error feedback control law and a linear time invariant trajectory feedforward control law. Experimental results of the proposed control law on the motion axes of a machining center, Matsuura MC510V, showed significant improvement of the contouring accuracy compared to the existing servo controller as well as the successful decoupling between the tangential dynamics and the normal (contouring) dynamics for feedrate up to 6 m/min (4 in/s).

A complete fault diagnostic system for automated vehicles operating in a platoon

Abstract: A "complete" fault diagnostic system is developed for automated vehicles operating as a platoon on an automated highway system. The diagnostic system is designed to monitor the complete set of sensors and actuators used by the lateral and longitudinal controllers of the vehicle, including radar sensors, magnetometers and inter-vehicle communication systems. A fault in any of the twelve sensors and three actuators is identified without requiring any additional hardware redundancy. The diagnostic system uses parity equations and several reduced-order nonlinear observers constructed from a simplified dynamic model of the vehicle. Nonlinear observer design techniques are used to guarantee asymptotically stable convergence of estimates for the nonlinear dynamic system. Different combinations of the observer estimates and the available sensor measurements are then processed to construct a bank of residues. The paper analytically shows that a fault in any one of the sensors or actuators creates a unique subset of these residues to grow so as to enable exact identification of the faulty component. Both simulation and experimental results are presented to demonstrate the effectiveness of the fault diagnostic system in the presence of various faults.

Rank minimization approach for solving BMI problems with random search

Abstract: Presents the rank minimization approach to solve general bilinear matrix inequality (BMI) problems. Due to the NP-hardness of BMI problems, no proposed algorithm that globally solves general BMI problems is a polynomial-time algorithm. We present a local search algorithm based on the semidefinite programming relaxation approach to indefinite quadratic programming, which is analogous to the well-known relaxation method for a certain-class of combinatorial problems. Instead of applying the branch and bound method for global search, a linearization-based local search algorithm is employed to reduce the relaxation gap. Furthermore, a random search approach is introduced along with the deterministic approach. Four numerical experiments are presented to show the search performance of the proposed approach.

Autonomous following lateral control of heavy vehicles using laser scanning radar

Abstract: Describes and compares some simple, easily applied solutions to the heavy vehicle autonomous following lateral control problem using a laser scanning radar unit. When mounted on the front of the following tractor, the sensor gives the relative displacement of the preceding trailer and the relative yaw between the following tractor and preceding trailer (although the ability to measure small relative yaw angles is quite limited). Given two vehicles within a platoon, there are two possible methods for interpolating a trajectory. One is linear and the other assumes constant curvature. Using these methods, the performance when tracking the preceding trailer with the following tractor's CG is compared to the case when the following tractor uses a measurement of the preceding tractor position as the reference. The results of simulations show the importance of using the same reference point on the preceding vehicle as the regulation point on the following vehicle.

Collision prediction and avoidance amidst moving objects for trajectory planning applications

Abstract: A methodology for computing a collision-free trajectory for mobile robots amidst moving objects is presented. This planner is based on a technique for computing the minimum translational distance between two mobile objects. This distance is then used for predicting and avoiding a collision. The computation of this distance is based on the application of the GJK algorithm to a particular subset of the Minkowski difference set of the involved objects. This subset states the separation or penetration distance between two objects along their given motions. When a collision is predicted, a collision-free intermediate temporal-position is generated avoiding such a collision.

Coordinated Longitudinal and Lateral Motion Control of Vehicles for IVHS

Abstract: In this paper, the authors present a systematic design for the combined control for vehicle longitudinal and lateral motions. They describe a fully coordinated control for steering and accelerating/braking actions which is used in maximizing the ability of distributing the traction forces in a set way. This control method covers a broad range of driving conditions. The authors also described the nominal traction force concept for handling unknown traction forces. In the presence of parametric uncertainties and uncertain nonlinearities, Robust Adaptive Control (RAC) by backstepping for MIMO nonlinear systems is used for controlling unmatched nonlinear vehicle dynamics.

Tuning of a Hard Disk Drive Servo Controller Using Fixed-Structure H∞ Controller Optimization

Abstract: To address the problem of improving the positioning accuracy of the read write head of hard disk drives (HDDs), we present a tuning methodology for the HDD servo controller based on the fixed-structure H∞ controller optimization. Since optimization is carried out under the fixed controller structure without any additional sensor, no extra cost is introduced. The effectiveness of the proposed method is demonstrated by simulation and experimentation.

H/sub /spl infin// optimization of Luenberger state observers and its application to fault detection filter design

Abstract: This paper considers H/sub /spl infin// optimization of Luenberger state observers. The conventional formulation of H/sub /spl infin//-optimal state observers does not allow the augmentation of dynamic performance weightings in the optimization objective, since it makes the problem a nonconvex optimization problem. We propose an algorithm to locally solve an H/sub /spl infin// optimization problem of Luenberger state observers by transforming the problem into an H/sub /spl infin// optimization problem of a static output feedback controller. The proposed approach offers an intuitive and efficient way to explicitly design the estimation error dynamics of the observer in the frequency domain. As an application example, the proposed approach is applied to the tuning of fault detection filters for lateral control of automated passenger vehicles. Numerical simulations are conducted to show the effectiveness of the proposed tuning method.

Robust Lateral Control of Heavy Duty Vehicles

Abstract: This report focuses on the robust lateral control of heavy vehicles for automated highway systems. The report first presents a coordinated steering and differential braking controller. An analogy is then made between a vehicle lateral control system and a mechanical system with the coulomb friction. Two feedforward compensators, combined with linear robust controller, are proposed for improving tracking performance of the linear feedback control systems. Through experiments, it is shown that a linear controller with feedforward compensation lifts the performance upper limit of the linear feedback control system and improves system performance. The report also presents solutions to the heavy vehicle autonomous following lateral control problem using a laser scanning radar unit. Using simulation results, it is shown that using the same reference point on the preceding vehicle as the regulation point on the following vehicle is important.

Design requirements and reference trajectory generation for a copier paperpath

Abstract: Presents an approach to introducing closed loop control in a copier paperpath in order to achieve robust, high-speed media handling. The basic idea exploits periodicity in the relative position of correctly fed sheets and their corresponding images. It is shown that the periodic behavior allows to design polynomial position reference trajectories for sheets as a function of their initial position error. Only longitudinal position errors are considered. By measuring sheet positions and using closed loop control to track the reference trajectories, position errors can be successfully removed. In addition to the reference trajectories, the paper also offers a design strategy that minimizes the required paperpath length while satisfying given bounds on sheet velocities and accelerations. Two examples, each with different initial error bounds, illustrate the design algorithm.

Reachability analysis of hybrid lateral control problem for automated heavy-duty vehicles

Abstract: In this paper, we conduct the reachability analysis for the safe set when the lateral control problem of automated heavy-duty vehicles is formulated as a hybrid automaton. Since the lateral control problem consists of lane following and lane changing, switching between these operating modes gives the closed-loop system a hybrid nature. The lateral controller is designed using H/sub /spl infin// loop-shaping method to ensure the robust performance under model uncertainties. It is designed to regulate the lateral deviation of the sensor output to zero under a lane following mode or make the lateral deviation to track a desired trajectory under a lane changing maneuver. Discrete states are given to represent different closed-loop systems for different operating modes. Worst case simulations are conducted to give the reachable sets for the lateral deviations on both nominal and perturbed plants. The results show that the reachable sets are in the safe region where the difference between the desired lateral deviation and the real lateral deviation is less than 0.2 m.

Multi-Rate Feedforward Tracking Control for Plants With Nonminimum Phase Discrete Time Models

Abstract: This paper deals with performance enhancement of tracking control systems by multi-rate control. The feedback controller is updated at the same rate as the sampling rate of the output measurements. The feedforward controller processes the desired output signal for high accuracy tracking, and its output is updated at a rate N-times faster than the sampling rate of the output measurements. The discrete time model of the controlled plant may possess unstable zeros, and the zero phase error tracking controller is used as a feedforward controller. Inter-sample behavior of the plant is included in evaluating the tracking performance of the multi-rate system. Illustrative examples are given to show advantages of the proposed multi-rate feedback/feedforward control scheme.

Robust tuning of fixed-structure controller for disk drives using statistical model and multi-objective genetic algorithms

Abstract: Proposes a non-gradient based method for the parameter optimization of fixed-structure controllers in hard disk drives (HDDs). Besides satisfying multiple frequency-domain constraints, the primary target of HDD servo design aims at the minimization of position error signal for a large population of drives. This is made possible by adopting a new statistical disturbance model inside the optimization loop to evaluate the time-domain performance of candidate controllers. The convexity of multi-dimension searching space is lost because the controller structure is fixed. This non-convex multiobjective optimization problem is solved by multiobjective genetic algorithms, which are genetic algorithms combined with the concept of Pareto optimality. Multiple optimal solutions with trade-offs are provided to support decision making. A design example of tuning a track following controller is used to demonstrate the effectiveness of the proposed method.

Asymptotic tracking for linear systems with actuator saturation by output feedback control

Abstract: This paper is concerned with asymptotic tracking for linear systems with actuator saturation by output feedback control. Both reference inputs and disturbances are represented as zero-input responses of linear systems. The controller includes the internal model with an anti-windup term for the reference and disturbance signals and a state observer for the system to allow output feedback control. The overall system is shown to be asymptotically stable for any initial condition of the system as long as the magnitudes of the reference and disturbance signals are sized such that the asymptotic tracking of the reference signal can be achieved without saturating the actuator. A simulation example is presented to verify the effectiveness of the proposed approach.

Simultaneous design of controller and fault detector and its application to motor drive control system

Abstract: This paper presents a simultaneous design strategy of controller and fault detector and its application to motor drive control systems. The influence of a fault in power electronic devices are analyzed and simulated. Experimental results demonstrate the effectiveness of the proposed design method.