Adaptive Control for Nonlinear Teleoperators With Uncertain Kinematics and Dynamics

Observer-based task-space consensus of networked robotic systems: A separation approach

“…In summary, the main contribution of our study here, as compared with the existing results for networked Euler-Lagrange systems or robotic systems (e.g., [5], [13], [9], [29], [28]) and also those in the context of bilateral teleoperation (see, e.g., [17], [37]), is to formalize the concept of manipulability followed by the systematic manipulability analysis concerning networked robotic systems and to address the case of no task-space velocity measurement by developing a new task-space observer. In particular, 1) we rigorously show that the gain of the integral action concerning the sliding vector (i.e., the weighted sum of the velocity and neighbor-to-neighbor position consensus errors) acts as a qualified measure of manipulability of the closed-loop system, and this provides a tuning freedom concerning the trade off between the manipulability and consensus equilibrium stability; 2) we also present a rigorous mathematical justification why the large damping yields the feeling of "sluggish" in teleoperator systems by using the measure of manipulability; 3) we illustrate by simulations and intuitive explanations that in a typical industrial/commercial robotic context, the integral action of the low-level PI velocity controller tends to decrease the manipulability of the system.…”

“…Therefore, various adaptive control algorithms are proposed to accommodate the kinematic uncertainties, using the estimated Jacobian matrix [23], [24]. The consensus schemes with consideration of the uncertain kinematics or both the uncertain kinematics and dynamics appear in [25], [26], [27], [28] (with the interaction graph being undirected) and in [9], [15] (with the interaction graph being directed and strongly connected). Motivated by the well-recognized fact that the task-space velocity measurement usually involves too much noise (due to the noisy nature of the task-space position measurement), the work in [29] gives an observerbased adaptive consensus scheme that does not require the task-space velocity measurement, where the observer explicitly relies on the joint velocity.…”

Nonlinear bilateral teleoperators under event‐driven communication with constant time delays

“…The communication delays were realized by using FIFO buffers for the transmitted packets, and the assigned communication delays were T m = 0.3 sec and T s = 0.2 sec. In the experimental setup, 46 both robots were connected to the same desktop computer, and force sensors were installed on the end-effector to measure external forces from human operator and remote environment. The gravitational force resulting from the manipulators and force sensors was precompensated precisely by the controllers with the use of dynamic model derived in the work of Liu and Chopra.…”

“…Consider the bilateral teleoperation system described in (1), (2) without the measurements of velocity signals under the assumption of passive external forces (6) and velocities (49). For the P-like controllers (46) and (47) together with velocity estimators (48), if the master and slave robots transmit their output signals over the communication network whenever the triggering conditions (50) and (51) are satisfied, respectively, then, for the range of gains and delays satisfying the condition that…”

Adaptive bilateral control of teleoperators with actuator uncertainty and quantized input

“…For the sake of avoiding chattering phenomenon and obtaining variable quantization levels along with the control input, hysteresis quantizer is adopted, and the robotic dynamics preceded by quantized inputs distinguish our work from the traditional teleoperator control schemes. [8][9][10][11][12][13][14][15][16][17]20,21 Via fully exploiting the structural feature of hysteresis quantizer and utilizing the sector-bound property, a novel decomposition-based method, which is inspired by the works by Zhou et al 25 and Wang et al, 28 is subsequently developed to cope with the control issue that only limited and quantized control inputs are available (see Theorem 1), for which the control design and stability analysis for the bilateral teleoperator system turn out to be feasible. 2.…”