Time Domain Passivity Control Approach Research Articles

Dual-Master/Single-Slave Haptic Teleoperation System for Semiautonomous Bilateral Control of Hexapod Robot Subject to Deformable Rough Terrain

The increasing application requirements of multilegged walking robots in outdoor environments pose new challenges regarding the design of their teleoperation systems. Some of these challenges arise from the multiple degrees of freedom of the telerobotic system and nonpassive exogenous disturbance. Herein, a novel control system based on a dual-master/single-slave bilateral haptic teleoperation framework using a semiautonomous strategy for hexapod robots walking on deformable rough terrains is proposed. In this teleoperation system, the body velocities and postures of the hexapod robot are determined according to the positions of two haptic master robots. The proposed teleoperator includes a time-domain passivity control approach to compensate for the system’s potential nonpassivity induced by the contact slippage between the foot and the ground. Furthermore, a posture-level bilateral controller is designed to overcome the unpredictable posture vibration. Information about the velocity loss and posture error is displayed to the human operator in the form of haptic force. In the underlying controller of the slave robot, a foot-force optimization algorithm is developed to improve the local autonomy of the teleoperation system. Furthermore, the stability of the system is demonstrated by its passivity. Experimental results indicate that the proposed controllers can provide a stable and transparent bilateral haptic teleoperation system for a hexapod robot under environmental perturbations.

Time domain passivity controller for 4-channel time-delay bilateral teleoperation.

This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.

Model-based passive bilateral teleoperation with time delay

Noisy behaviour of time domain passivity control (TDPC) at low velocity is a well known problem for delayed teleoperation systems. This paper presents a novel adaptive model-based passive controller to alleviate some of the noise problems associated with delayed teleoperation system using the TDPC approach. By composing an online estimation of phantom human tissue model and passivity observer on the master side, a high transparency of teleoperation can be achieved while the system passivity is maintained by modifying the damping of the master. The performance of the developed approach was validated using one-degree-of-freedom master–slave robot system with constant time delay. Results show that the phantom tissue parameters can be accurately estimated. In addition, the passivity of the system is observed by the passivity observer using the output of the identified tissue model. Results demonstrate that stable teleoperation with time delay can be achieved and the environment force can be accurately reflected to the operator without chattering.

Bilateral Teleoperation With Time-Varying Delay: A Communication Channel Passification Approach

In this paper, the activeness of bilateral communication with time-varying delay is analyzed. Based on the power-based time-domain passivity control previously proposed, a time-domain passivity control approach is derived for bilateral communication. Teleoperation experimental results verify the effectiveness.

Passivity control of a haptic device for the simulation of knobs

Knobs are one of the details from which household appliances are commonly judged by the customers. Although very subjective, the customers’ requirements reflect real needs, such as robustness and easy use; therefore the design of knobs and buttons, that are the most widely used end-user interfaces, is of utmost importance from the commercial point of view and requires careful investigation. A mechatronic device has been designed to simulate the knobs’ behaviour for supporting an extensive campaign of end-users tests. The impedance control approach is applied exploiting a model of the actuator. However, as the acceleration information is extracted through double differentiation of position measurements, the inertia cannot be compensated; this can sometimes compromise the stability. The stability problem is therefore addressed through the time-domain passivity control approach, which guarantees stability and is easy to implement, but produces a slight decrease in performance, namely a mismatch between desired and real torque.

Time Domain Passivity Control for Position-Position Teleoperation Architectures

This article presents a method for passivating the communication channel of a symmetric position-position teleoperation architecture on the time domain. The time domain passivity control approach has recently gained appeal in the context of timedelayed teleoperation because passivity is not established as a design constraint, which often forces conservative rules, but rather as a property which the system must preserve during operation. Since passivity is a network property, the first design rule within this framework is to represent consistent and comprehensible circuit (i.e., network) representations of the mechanical teleoperation system. In particular, the energetic behavior of these networks is interesting because it allows straightforward conclusions about system stability. By means of so-called passivity observers (PO) and passivity controllers (PC) (Hannaford & Ryu, 2001), the energetic response of a delayed communication channel is captured and modulated over time so that the network in question never becomes nonpassive. The case analyzed in this paper tackles a communication channel that conveys position data back and forth. This type of channel does not offer intuitive network representation since only flows are actually being transmitted. Although energy clearly travels from one side to the other, port power identification, as defined by the correlated pair flow and effort, is not evident. This work first investigates how this kind of channel can be represented by means of circuit networks even with the lack of physical effort being transmitted through the channel, and identifies which networks are susceptible to become nonpassive due to the channel characteristics (i.e., time delay, discretization or package loss). Once achieved, a distributed control structure is presented based on a PC series that keeps the system at the verge of passivity (and therefore stability) independent from the channel properties. The results obtained by the simulation and by experiment sustain the presented approach.

Landing Force Control for Humanoid Robot by Time-Domain Passivity Approach

This paper proposes a control method to absorb the landing force or the ground reaction force for a stable dynamic walking of a humanoid robot. Humanoid robot may become unstable during walking due to the impulsive contact force of the sudden landing of its foot. Therefore, a control method to decrease the landing force is required. In this paper, time-domain passivity control approach is applied for this purpose. Ground and the foot of the robot are modeled as two one-port network systems that are connected, and exchange energy with each other. The time-domain passivity controller with admittance causality is implemented, which has the landing force as input and foot's position to trim off the force as output. The proposed landing force controller can enhance the stability of the walking robot from simple computation. The small-sized humanoid robot, HanSaRam-VII that has 27 DOFs, is developed to verify the proposed scheme through dynamic walking experiments.

Stability Guaranteed Control: Time Domain Passivity Approach

A general framework for expanding the time-domain passivity control approach, to large classes of control systems is proposed. We show that large classes of control systems can be described from a network point of view. Based on the network presentation, the large classes of control systems are analyzed in a unified framework. In this unified network model, we define input energy, which is a virtual source of for control, and real output energy that is physically transferred to a plant to allow the concept of passivity to be used to study the stability of large classes of control systems. For guaranteeing the stability condition, the time-domain passivity controller for two-port is applied. Design procedure is demonstrated for a motion control system. The developed method is tested with numerical simulation in the regulation of a single link flexible manipulator. Totally stable control is achieved under wide variety of operating condition and uncertainties without any model information.