Jingang Yi

Disturbance-Observer-Based Hysteresis Compensation for Piezoelectric Actuators

We present a novel hysteresis compensation method for piezoelectric actuators. We consider the hysteresis nonlinearity of the actuator as a disturbance over a linear system. A disturbance observer (DOB) is then utilized to estimate and compensate for the hysteresis nonlinearity. In contrast to the existing inverse-model-based approach, the DOB-based hysteresis compensation does not rely on any particular hysteresis model, and therefore provides a simple and effective compensation mechanism. We design and fabricate a lead magnesium niobate-lead titanate (PMN-PT) piezoelectric actuator for microscale tip-based power sintering process. Experimental validation of the proposed hysteresis compensation is performed on the PMN-PT cantilever piezoelectric actuator. The experimental results demonstrate the effectiveness and efficiency of the approach.

Multicluster tools scheduling: an integrated event graph and network model approach

Steady-state throughput and scheduling of a multicluster tool become complex as the number of modules and clusters grows. We propose a new methodology integrating event graph and network models to study the scheduling and throughput of multicluster tools. A symbolic decision-move-done graph modeling is developed to simplify discrete-event dynamics for the multicluster tool. This event graph is further used for searching feasible action sequences of the cluster tool. By representing sequences with networks, an extended critical path method is applied to calculate the corresponding cycle time. Grouping methods that are based on network are also introduced to reduce the searching complexity. Compared with optimization-based scheduling approaches, the proposed methodology can directly capture the cyclic characteristic of cluster tool schedules and be applied to analyze the impact of process and wafer flow variations on cycle time and robot schedules. We have successfully applied this new methodology to dozens of cluster tools at Intel Corporation. A chemical-mechanical planarization polisher is employed as an example to illustrate and validate the proposed methodology

Adaptive emergency braking control with underestimation of friction coefficient

In this paper, a control scheme for emergency braking maneuvers in automated highway systems and a new online identification scheme to determine the tire-road friction characteristics of the vehicle are presented. The proposed controller determines the required pressure in the master cylinder of the braking system to achieve maximum deceleration during braking, based on the estimation of the tire-road friction characteristics and the overall braking system gain, for the given set of parameter estimates. With persistence of excitation, the identified static map between the tire longitudinal slip and the tire-road friction coefficient is guaranteed to converge to the actual map. When there is no persistence of excitation, and under a proper choice of initial conditions and adaptation gains, the proposed scheme underestimates the maximum coefficient of friction and its corresponding slip, and allows a conservative calculation of the safety critical inter-vehicle spacing.

Optimal Scheduling of Multicluster Tools With Constant Robot Moving Times, Part I: Two-Cluster Analysis

In semiconductor manufacturing, finding an efficient way for scheduling a multicluster tool is critical for productivity improvement and cost reduction. This two-part paper analyzes optimal scheduling of multicluster tools equipped with single-blade robots and constant robot moving times. In this first part of the paper, a resource-based method is proposed to analytically derive closed-form expressions for the minimal cycle time of two-cluster tools. We prove that the optimal robot scheduling of two-cluster tools can be solved in polynomial time. We also provide an algorithm to find the optimal schedule. Examples are presented to illustrate the proposed approaches and formulations.

Steady-State Throughput and Scheduling Analysis of Multicluster Tools: A Decomposition Approach

Cluster tools are widely used as semiconductor manufacturing equipment. While throughput analysis and scheduling of single-cluster tools have been well-studied, research work on multicluster tools is still at an early stage. In this paper, we analyze steady-state throughput and scheduling of multicluster tools. We consider the case where all wafers follow the same visit flow within a multicluster tool. We propose a decomposition method that reduces a multicluster tool problem to multiple independent single-cluster tool problems. We then apply the existing and extended results of throughput and scheduling analysis for each single-cluster tool. Computation of lower-bound cycle time (fundamental period) is presented. Optimality conditions and robot schedules that realize such lower-bound values are then provided using ldquopullrdquo and ldquoswaprdquo strategies for single-blade and double-blade robots, respectively. For an -cluster tool, we present lower-bound cycle time computation and robot scheduling algorithms. The impact of buffer/process modules on throughput and robot schedules is also studied. A chemical vapor deposition tool is used as an example of multicluster tools to illustrate the decomposition method and algorithms. The numerical and experimental results demonstrate that the proposed decomposition approach provides a powerful method to analyze the throughput and robot schedules of multicluster tools.

Dynamic Friction Model-Based Tire-Road Friction Estimation and Emergency Braking Control

An adaptive control scheme for emergency braking of vehicles is designed based on a LuGre dynamic model for the tire-road friction. The wheel angular speed and longitudinal vehicle acceleration information are used to design a fast convergence observer to estimate the vehicle velocity and the internal state of the friction model. The unknown parameters of the dynamic friction model are estimated through a parameter adaptation law. A Lyapunov-based state estimator and a stabilizing braking controller are designed to achieve near to maximum braking capability of the vehicle. Underestimation of the maximum friction coefficient, a very desirable feature from the perspective of safety, is guaranteed by a proper choice of adaptation gains and initial values of the estimated friction parameters. fDOI: 10.1115/1.1870036g

Kinematic Modeling and Analysis of Skid-Steered Mobile Robots With Applications to Low-Cost Inertial-Measurement-Unit-Based Motion Estimation

Skid-steered mobile robots are widely used because of their simple mechanism and high reliability. Understanding the kinematics and dynamics of such a robotic platform is, however, challenging due to the complex wheel/ground interactions and kinematic constraints. In this paper, we develop a kinematic modeling scheme to analyze the skid-steered mobile robot. Based on the analysis of the kinematics of the skid-steered mobile robot, we reveal the underlying geometric and kinematic relationships between the wheel slips and locations of the instantaneous rotation centers. As an application example, we also present how to utilize the modeling and analysis for robot positioning and wheel slip estimation using only low-cost strapdown inertial measurement units. The robot positioning and wheel slip-estimation scheme is based on an extended Kalman filter (EKF) design that incorporates the kinematic constraints for accuracy enhancement. The performance of the EKF-based positioning and wheel slip-estimation scheme are also presented. The estimation methodology is tested and validated experimentally on a robotic test bed.

Emergency Braking Control with an Observer-based Dynamic Tire/Road Friction Model and Wheel Angular Velocity Measurement

Summary A control scheme for emergency braking of vehicles is designed. The tire/road friction is described by a LuGre dynamic friction model. The control system output is the pressure in the master cylinder of the brake system. The controller utilizes estimated states for a feedback control law that achieves a near maximum deceleration. The state observer is designed using linear matrix inequality (LMI) techniques. The analysis shows that using the wheel angular speed information exclusively is not sufficient to rapidly estimate the velocity and relative velocity, due to the fact that the dynamical system is almost unobservable with this measurement as output. Findings are confirmed by simulation results that show that the estimated vehicle velocity and relative velocity converge slowly to their true values, even though the internal friction state and friction parameters converge quickly. The proposed control system has two main advantages when compared with an antilock braking system (ABS): (1) it produces a source of a priori information regarding safe spacing between vehicles that can be used to increase safety levels in the highway; and (2) it achieves a near optimal braking strategy with less chattering.

Trajectory tracking and balance stabilization control of autonomous motorcycles

We report a new trajectory tracking and balancing control algorithm for an autonomous motorcycle. Building on the existing modeling work of a bicycle, the new dynamic model of the autonomous motorcycle considers the bicycle caster angle and captures the steering effect on the vehicle tracking and balancing. The trajectory tracking control takes an external/internal model decomposition approach. A nonlinear controller is designed to handle the vehicle balancing. The motorcycle balancing is guaranteed by the system internal equilibria calculation and by the trajectory and system dynamics requirements. The proposed control system is validated by numerical simulations, and is based on a real prototype motorcycle system

Optimal Scheduling of Multicluster Tools With Constant Robot Moving Times, Part II: Tree-Like Topology Configurations

In this paper, we analyze optimal scheduling of a tree-like multicluster tool with single-blade robots and constant robot moving times. We present a recursive minimal cycle time algorithm to reveal a multi-unit resource cycle for multicluster tools under a given robot schedule. For a serial-cluster tool, we provide a closed-form formulation for the minimal cycle time. The formulation explicitly provides the interaction relationship among clusters. We further present decomposition conditions under which the optimal scheduling of multicluster becomes much easier and straightforward. Optimality conditions for the widely used robot pull schedule are also provided. An example from industry production is used to illustrate the analytical results. The decomposition and optimality conditions for the robot pull schedule are also illustrated by Monte Carlo simulation for the industrial example.