Improvement of model-mediated teleoperation using a new hybrid environment estimation technique

Abstract

In a haptic teleoperation system, the incorporation of knowledge about the remote environment in the controller design can improve stability and performance. Model-mediated teleoperation adopts this idea by rendering an estimated model of the remote environment on local site instead of transmitting force/velocity flows. Thus, the user perceives locally generated forces corresponding to the estimated and transmitted model parameters and the control loop between master and slave is opened. Less conservative stability boundaries and the applicability to teleoperation systems with arbitrary time delay are the main advantages of this approach. In order to guarantee a high fidelity, the estimation has to fit well with the measurements. In this paper, we extend the approach of modelmediated teleoperation to a full 6 degrees-of-freedom (DOF) teleoperation system with negligible time delay. We furthermore propose a hybrid approach for the estimation of the remote environment by combining the classical Kelvin-Voigt model and the nonlinear Hunt-Crossley model. Persistent excitation and device-dependent limitations of the estimation algorithm are discussed. Experimental results show stability and accuracy of the estimation technique as well as a superior fidelity of the proposed approach compared to a position-based admittance controller with fixed parameters even with negligible time delay.

Increasing stability in model-mediated teleoperation approach by reducing model jump effect

“…Although hard and soft are intrinsically qualitative terms, it is common in the literature to assume an environment with stiffness bigger than 2500 N/m (i.e. 2500 K N m ) as hard and otherwise as soft [15,20]. For damping coefficient, however, such a general convention does not exist; but it seems a good estimation to consider the ratio 1 …”

“…The selection of the proper model between KV and HC for the environment is carried out by the hybrid object modeling approach which is proposed in [15] and augmented in [16]. This approach is represented by the S operator…”

Point Cloud-Based Model-Mediated Teleoperation With Dynamic and Perception-Based Model Updating

“…One of the main tasks of a MMT system is to estimate the environment parameters [16][17][18][19][20][21][22][23][24]. In [16], a damper-spring model is adopted to approximate the environment, and a sliding average least-square algorithm is proposed to estimate the dynamic parameters of the environment on the slave side for online updating of the virtual model parameters on the master side in the presence of large communication delay.…”

Point-cloud-based model-mediated teleoperation

“…One of the main tasks of a MMT system is to estimate the environment parameters [16][17][18][19][20][21][22][23][24]. In [16], a damper-spring model is adopted to approximate the environment, and a sliding average least-square algorithm is proposed to estimate the dynamic parameters of the environment on the slave side for online updating of the virtual model parameters on the master side in the presence of large communication delay.…”

“…Both estimation approaches, however, work only for one degree-of-freedom (DoF) systems. A multi-DoF estimation method is proposed in [18,19], where physical properties such as stiffness and damping are estimated in real-time. Yet, the communication delay as well as the surface friction is ignored.…”