An application of IMPACT structure to bilateral teleoperations

Time-delays typically cause stability and performanceproblems in teleoperation systems. As a remedy forsuch problems in position-error based bilateralteleoperations, a control algorithm is proposed which isderived as a robust modification of a Smith predictorstructure for time delay compensation. The consideredmodification is based on an application of the InternalModel Principle And Control Together (IMPACT). Theresulting algorithm allows rejection of disturbances from aknown class, that act at the output of the slave. Lineardynamics are considered for both master and slavemanipulators and it is assumed that the time-delay dueto communication is constant and known upto a certaindegree of accuracy. The algorithm is illustrated insimulations

Cooperative manipulation with unilateral constraints

Cooperative manipulation provides multiple robots the capability to perform tasks that are difficult or even impossible to be executed by a single manipulator. Among these tasks are, for instance, carrying heavy or large payloads, conducting multi-part assembly, and handling of flexible objects. If a large object with no special features (e.g. handle) will be manipulated, the object may not be grasped rigidly and relative motion between the manipulators and the object mayoccur. When the robots are initially not in contact with the manipulated object and brought to contact to perform the desired manipulation task, there will be a change in the dynamics of the system due to contact. Furthermore, according to the relative motion between the robots and the object, the contact condition can change from rolling to sliding contact. Besides that when the 3-dimensional case with only rolling contacts is considered, the constraints are nonholonomic. The control objectives in such cooperative tasks is not only to control the position of the object, but also to accomodate the internal forces (or stresses) and external contact forces between the object and the environment

Time delay compensation in bilateral teleoperations using IMPACT

Teleoperated systems may be subject to destabilizing and performance degrading effects due to time delays. An appealing remedy is an application of the internal model principle and control together (IMPACT) structure as it is done in this paper in the problem of position-error-based bilateral teleoperation. The IMPACT algorithm proposed in this paper allows time-delay compensation and rejection of disturbances from a known class that act at the output of the slave manipulator. Simulation and experimental results illustrate the effectiveness of the algorithm

Internal and external force-based impedance control for cooperative manipulation

An asymptotically stable cascaded control algorithm is proposed for cooperative manipulation of a common object. This algorithm controls motion and internal forces of the object, as well as the contact forces between the object and environment. The motion of each manipulator is controlled using an inverse dynamics type of controller. Only knowledge of the kinematics of the manipulated object is required, since the interaction forces and moments between the object and manipulators are measured. The internal stresses in the object are controlled based on enforced impedance relationships between the object and each manipulator. The internal forces and moments are computed using the object kinematics. Contact with the environment is controlled with an enforced impedance relationship between the object and the environment. For both internal and external forces, reference trajectories can be specified. Asymptotic stability of each controller is proven using Lyapunov stability theory and LaSalle’s invariance principle. Guidelines are suggested to compute control parameters of the internal impedance parameters. Merits of the control algorithm are demonstrated in simulations

Application of the IMPACT structure on bilateral teleoperation

A common issue encountered in teleoperation systems is a time-delay in the communication channel. Depending onthe type of communication protocol, the delay can be constant or time-varying. In both cases, the delay can seriously degrade performance of teleoperations or even destroy stability. In this work, we apply the IMPACT approach to position error (PERR) based teleoperations, where only position information is exchanged between the master and slave manipulators. Our method combines a Smith predictor with a disturbance estimator designed based on an expected class of disturbances acting at the output of the slave manipulator

Internal and external force-based impedance control for cooperative manipulation

An asymptotically stable cascaded control algorithm is proposed for cooperative manipulation of a common object. This algorithm controls motion and internal forces of the object, as well as the contact forces between the object and environment. The motion of each manipulator is controlled using an inverse dynamics type of controller. Only knowledge of the kinematics of the manipulated object is required, since the interaction forces and moments between the object and manipulators are measured. The internal stresses in the object are controlled based on enforced impedance relationships between the object and each manipulator. The internal forces and moments are computed using the object kinematics. Contact with the environment is controlled with an enforced impedance relationship between the object and the environment. For both internal and external forces, reference trajectories can be specified. Asymptotic stability of each controller is proven using Lyapunov stability theory and LaSalle’s invariance principle. Guidelines are suggested to compute control parameters of the internal impedance parameters. Merits of the control algorithm are demonstrated in simulations

Application of the IMPACT structure on bilateral teleoperation

A common issue encountered in teleoperation systems is a time-delay in the communication channel. Depending onthe type of communication protocol, the delay can be constant or time-varying. In both cases, the delay can seriously degrade performance of teleoperations or even destroy stability. In this work, we apply the IMPACT approach to position error (PERR) based teleoperations, where only position information is exchanged between the master and slave manipulators. Our method combines a Smith predictor with a disturbance estimator designed based on an expected class of disturbances acting at the output of the slave manipulator