Discrete-Time H-Infinity Synthesis of Frequency-Shaped Sliding Mode Control for Suppression of Vibration With Multiple Peak Frequencies

Vibration with multiple large peaks at high frequencies may cause significant performance degradation and have become a major concern in modern high precision control systems. To deal with such high-frequency peaks, it is proposed to design a frequency-shaped sliding mode controller based on H∞ synthesis. It obtains an ‘optimal’ filter to shape the sliding surface, and thus provides frequency-dependent control allocation. The proposed frequency-shaping method assures the stability in the presence of multiple-peak vibration sources, and minimizes the weighted H∞ norm of the sliding surface dynamics. The evaluation is performed on a simulated hard disk drive with actual vibration sources from experiments, and the effectiveness of large vibration peak suppression is demonstrated.

Settling Control of the Triple-Stage Hard Disk Drives Using Robust Output Feedback Model Predictive Control

Track settling control for a hard disk drive with three actuators has been considered. The objective is to settle the read/write head on a specific track by following the minimum jerk trajectory. Robust output feedback model predictive control methodology has been utilized for the control design which can satisfy actuator constraints in the presence of noises and disturbances in the system. The controller is designed based on a low order model of the system and has been applied to a higher order plant in order to consider the model mismatch at high frequencies. Since the settling control generally requires a relatively low frequency control input, simulation result shows that the head can be settled on the desired track with 10 percent of track pitch accuracy while satisfying actuator constraints.

Implementation of State and Disturbance Estimation for Quadrotor Control Using Extended High-Gain Observers

This paper proposes a discrete-time, multi-time-scale estimation and control design for quadrotors in the presence of external disturbances and model uncertainties. Assuming that not all state measurements are available, they will need to be estimated. The sample-data Extended High-Gain Observers are used to estimate unmeasured states, system uncertainties, and external disturbances. Discretized dynamic inversion utilizes those estimates and deals with an uncertain principal inertia matrix. In the plant dynamics, the proposed control forces the rotational dynamics to be faster than the translational dynamics. Numerical simulations and experimental results verify the proposed estimation and control algorithm. All sensing and computation is done on-board the vehicle.

Downshifting Control Strategy for Dual Clutch Transmission With Single Clutch Slippage

The cooperation mode between the engagement and disengagement clutches for vehicles equipped with Dual Clutch Transmission (DCT) is of vital importance to achieve a smooth gearshift, in particular for the downshift process as its unavoidable power interruption during the inertia phase. Hence, to elevate the performance of DCT downshifting process, an analytical model and experimental validation for the analysis, simulation and control strategy are presented. Optimized pressure profiles applied on two clutches are obtained based on the detailed analysis of downshifting process. Then, according to the analysis results, a novel control strategy that can achieve downshift task with only one clutch slippage is proposed. The system model is established on Matlab/Simulink platform and used to study the variation of output torque and speed in response to different charging pressure profiles and various external loads during downshifting process. Simulation results show that, compared with conventional control strategies, the proposed one can not only avoid the torque hole and power circulation, but shorten the shift time and reduce the friction work. Furthermore, to validate the effectiveness of the control strategy, the bench test equipped with DCT is conducted and the experiment results show a good agreement with the simulation results.

Autonomous Charging for an Underwater Robotic Fish by Direct Contact

The operation of autonomous underwater vehicles is often hindered by their battery capacity, limiting the duration of its use. Here, we propose an integrated solution for autonomous charging of a robotic fish via direct contact through a novel claw mechanism for docking guidance. To assist the robotic fish in the docking process, the system incorporates a charging station designed with form-fit claws. A controller is designed to monitor the battery level of the robotic fish during free swimming and coordinate the docking process with respect to the maneuvers of both the robot and form-fit claws. Upon recognizing a low battery level, the controller commands the robotic fish to begin the docking process, and video feedback from an overhead camera is used to inform the autonomous navigation toward the charging station. After reaching a battery level threshold, the robotic fish is then released back in the water and returns to free swimming until the battery is discharged again. Through a series of experiments, we demonstrate the possibility of prolonged operation, consisting of repeated cycles of autonomous charging. Our proposed charging method enables prolonged autonomous swimming with minimal human supervision, opening the door for new, transformative applications of robotic fish in laboratory research and field deployment.

A ROS-Simulink Real-Time Communication Bridge Using UDP With a Driver-in-the-Loop Application

This paper presents implementation details and performance metrics for software developed to connect the Robot Operating System (ROS) with Simulink Real-Time (SLRT). The communication takes place through the User Datagram Protocol (UDP) which allows for fast transmission of large amounts of data between the two systems. We use SLRT’s built-in UDP communication and binary packing blocks to send and receive the data over a network. We use implementation metrics from several examples to illustrate the effectiveness and drawbacks of this bridge in a real-time environment. The time latency of the bridge is analyzed by performing loop-back tests and obtaining the statistics of the time delay. A proof of concept experiment is presented that utilizes two laboratories that ran a driver-in-the-loop system despite a large physical separation. This work provides recommendations for implementing data integrity measures as well as the potential to use the system with other applications that demand high speed real-time communication.

Efficient Optical Localization for Mobile Robots via Kalman Filtering-Based Location Prediction

Localization and communication are both essential functionalities of any practical mobile sensor network. Achieving both capabilities through a single Simultaneous Localization And Communication (SLAC) would greatly reduce the complexity of system implementation. In this paper a technique for localizing a mobile agent using the line of sight (LOS) detection of an LED-based optical communication system is proposed. Specifically, in a two-dimensional (2D) setting, the lines of sight between a mobile robot and two base nodes enable the latter to acquire bearing information of the robot and compute its location. However, due to the mobile nature of the robot, establishing its LOS with the base nodes would require extensive scan for all parties, severely limiting the temporal resolution and spatial precision of the localization. We propose the use of a Kalman filter to predict the position of the robot based on past localization results, which allows the nodes to significantly reduce the search range in establishing LOS. Simulation results and preliminary experimental results are presented to illustrate and support the proposed approach.

Real-Time Powertrain Optimization Strategy for Connected Hybrid Electrical Vehicle

Connected Vehicle (CV) technology, which allows traffic information sharing, and Hybrid Electrical Vehicles (HEV) can be combined to improve vehicle fuel efficiency. However, transient traffic information in CV environment necessitates a fast HEV powertrain optimization for real-time implementation. Model Predictive Control (MPC) with Linearization is proposed, but the computational effort is still prohibitive. The Equivalent Consumption Minimization Strategy (ECMS) and Adaptive-ECMS are proposed to minimize computation time, but unable to guarantee charge-sustaining-operation (CS). Fast analytical result from Pontryagin’s Minimum Principles (PMP) is possible but the input has to be unconstrained. Numerical solutions with Linear Programming (LP) are proposed, but over-simplifications of the cost and constraint functions limit the performance of such methods. In this paper, a nonlinear CS constraint is transformed into linear form with input variable change. With linear input and CS constraints, the problem is solved with Separable Programming by approximating the nonlinear cost with accurate linear piecewise functions which are convex. The piecewise-linear functions introduce new dimensionless variables which are solved as a large-dimension constrained linear problem with efficient LP solvers. Comparable fuel economy with Dynamic Programming (DP) is shown, with maximum fuel savings of 7% and 21.4% over PMP and Rule-Based (RB) optimizations. Simulations with different levels of vehicle speed prediction uncertainties to emulate CV settings are presented.

A Two-Level Adaptive Fuzzy Control Algorithm for Beyond Pull-In Stabilization of Electrostatically Actuated Microplates

The objective of this paper is to present an adaptive multi-level fuzzy controller to stabilize the deflection of an electrostatically actuated microplate beyond its pull-in range. Using a single mode approximation along with utilizing the Lagrange equations, the dynamic behavior of the microplate is described in modal space by an ordinary differential equation. By different static and dynamic simulations, the system and the dependence of the deflection to the input applied voltage is identified linguistically. Then, based on the linguistic description of the system, a fuzzy controller is designed to stabilize the microplate at the desired deflections. To improve the performance specifications of the closed-loop system, another fuzzy controller at a higher level is designed to adjust the parameters of the main controller in real time. The simulation results reveal that by using the proposed single level and adaptive two level controllers, the control objective is met effectively with good performance specifications. It is also observed that adding a supervisory level to the main controller can reduce the overshoot and the settling time in beyond pull-in stabilization of electrostatically actuated microplates. The qualitative knowledge resulting from this research can be generalized and used for development of efficient controllers for N/MEMS actuators and electrostatically actuated nano/micro positioning systems.

A Modular 2-DOF Serial Robot Manipulator for Education in Robot Control

This paper describes a modular 2-DOF serial robot manipulator and accompanying experiments that have been developed to introduce students to the fundamentals of robot control. The robot is designed to be safe and simple to use, and to have just enough complexity (in terms of nonlinear dynamics) that it can be used to showcase and compare the performance of a variety of textbook robot control techniques including computed torque feedforward control, inverse dynamics control, robust sliding-mode control, and adaptive control. These various motion control schemes can be easily implemented in joint space or operational space using a MATLAB/Simulink real-time interface. By adding a simple 2-DOF force sensor to the end-effector, the robot can also be used to showcase a variety of force control techniques including impedance control, admittance control, and hybrid force/position control. The 2-DOF robots can also be used in pairs to demonstrate control architectures for multi-arm coordination and master/slave teleoperation. This paper will describe the 2-DOF robot and control hardware/software, illustrate the spectrum of robot control methods that can be implemented, and show sample results from these experiments.