Masood Dehghan

Brief paper: Discrete-time switching linear system with constraints: Characterization and computation of invariant sets under dwell-time consideration

This paper introduces the concepts of Dwell-Time invariant/contractive (DT-invariant/contractive) set, Constraint Admissible DT-invariant/contractive (CADT-invariant/contractive) set for a discrete-time switching system under dwell-time switching. Main contributions of this paper include a characterization for a DT-contractive set, an algorithm for the computation of the maximal CADT-invariant set, a necessary and sufficient condition for asymptotic stability of the origin of switching systems under dwell-time switching and computation of the minimal dwell-time needed for asymptotic stability of the origin.

Characterization and computation of disturbance invariant sets for constrained switched linear systems with dwell time restriction

This paper introduces the concept and characterization of Disturbance-Dwell-Time invariance (DDT-invariance) and Constraint Admissible DDT-invariance (CADDT-invariance) for constrained systems with additive disturbance under dwell-time switching. Using the characterization, necessary and sufficient conditions for DDT-invariance and algorithms for the computation of the minimal and maximal constraint admissible convex DDT-invariant sets are provided. Numerical examples of such sets for several systems are also provided.

Computations of mode-dependent dwell times for discrete-time switching system

Given a system that switches among N linear subsystems, this paper shows an approach that computes N dwell times, one for each of the subsystems, such that the overall system is stable under switching signals that respect the dwell times. The dwell times are obtained progressively starting from the groups of all pairwise switching systems, and increasing the size of the group by one for each step. In each progressive step, a bisection search algorithm is used to obtain the mode-dependent dwell times for that step. When the final step is reached, the N-mode dwell times are obtained. These dwell times are smaller, in terms of their sum, than an existing approach in recent literature for all the examples considered in this paper.

Discrete-time switched linear system with constraints: Characterization and computation of invariant sets under dwell-time consideration

This paper introduces the concepts of Dwell-Time invariance (DT-invariance) and maximal constraint admissible DT-invariant set for discrete-time switching systems under dwell-time switching. Main contributions of this paper include a characterization for DT-invariance; a numerical computation of the maximal CADT-invariant set; a necessary and sufficient condition for asymptotic stability of the origin of the switching systems under dwell time switching and an algorithm for the computation of the minimal dwell time needed for stability.

Model Predictive Control for Switching Systems With Dwell-Time Restriction

This work proposes a model predictive control (MPC) approach for a switching linear system where the switching signal is prescribed with unknown future values. The switching signal is known only at its current value, satisfies a minimal dwell-time restriction of τ steps between successive switchings and is otherwise arbitrary. Under such a setting, the MPC optimization problem has to allow for all admissible switching sequences within a given horizon length. Such a formulation necessitates several other features: the use of a modified returnable set as the terminal constraint; the introduction of consistency constraints on the predicted controls; a min-max optimization criterion as the cost function; the splitting of the horizon into two portions for recursive feasibility consideration and exponential stability of the closed-loop system. The proposed approach is demonstrated by a numerical example.

Enlarging domain of attraction of switched linear systems in the presence of saturation nonlinearity

This work proposes an approach to compute domain of attraction of switched systems under arbitrary switching and in the presence of saturation nonlinearity. It is also shown that any estimation of domain of attraction using linear difference inclusion approaches is a subset of our result and hence our method is less conservative than the others.

Characterization and computation of robust invariant sets for switching systems under dwell-time consideration

This paper introduces the concept of Disturbance-Dwell-Time invariance (DDT-invariance) for constrained switching systems with additive disturbance under dwell-time switching. This concept is useful for the characterization of invariant sets for such systems. Necessary and sufficient conditions for DDT-invariance of a set are also provided and algorithms for the numerical computation of the minimal and maximal constraint admissible convex DDT-invariant sets are proposed.

Real-time human-robot interaction in complex environment using kinect v2 image recognition

This paper presents real-time interaction between 7-DOF KUKA robotic arm and any untrained human operator using Kinect V2. Kinect sensor is utilized to detect human body joints and mono color object to be grasped, using HSL-XYZ algorithm. By moving hand holding simple object such as a ball, operator can make KUKA robot follow the expected trajectory and fulfill pass-and-place tasks. One hand of operator is followed by KUKA, while the pose of the other arm commands the gripper to move, grasp, release and place. Experiments proved our advantages that Human-Robot Interaction is more robust, easier and more intuitive for human, with lower requirements for sensor; and is a novel solution for industries and life. Client - server application using UDP protocol is performed to transmit and receive real-time control and feedback data.

Characterization of switching sequences on system with dwell-time restriction for Model Predictive Control

This work proposes a Model Predictive Control (MPC) approach for a switching discrete-time linear system where the switching signal is prescribed but its future values are unknown except that at the current time. The switching signal satisfies a minimal dwell time restriction of τ steps between successive switchings (including the case of τ = 1) and is otherwise arbitrary. Under such a setting, the MPC optimization problem has to allow for all admissible switching sequences within a given horizon length. Such a formulation necessitates several other features. These include the use of a modified returnable set as the terminal constraint; the introduction of consistency constraints on the predicted controls for recursive feasibility consideration; a min-max optimization criterion as the cost function; the splitting of the horizon length into two portions for recursive feasibility consideration and exponential stability of the closed-loop system. The proposed approach is demonstrated by numerical example.

An Impedance Controller for Surface Alignment

This paper present a human-inspired compliant surface to surface alignment method for robotic manipulators. The surface alignment task is break down into several stages, a) make a point contact, b) alignment of point-contact to line-contact, and finally c) surface to surface alignment. The proposed controller is a combination of impedance control with rotational controllers that are activated based on the force sensing from the robot. We evaluate the performance of the proposed controller on a set of robot experiments using a 7-DOF KUKA iiwa robot on an inclined surface with different angles.