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This paper presents the robust control scheme of improving the poor tracking performance owing to the defects of the time-delayed control (TDC) for robot manipulators. The defects of TDC include inaccurate estimation of an inertia matrix model and joint accelerations required to formulate the TDC scheme. The accuracy of estimating the inertia matrix and accelerations plays an important role in the control performance as well as the stability of TDC. To improve the estimation, the inertia matrix is identified by the recursive least square (RLS) method and the acceleration signals are estimated by a state observer (SOB). Tracking control performances of a manipulator by the proposed scheme are empirically tested and compared.

The time-delayed control (TDC) requires the inertia model and acceleration signals as well as the previous torque information of the robot manipulator. Performances of TDC depends on the accuracy of the estimation of inertia and acceleration signal. Therefore, more accurate estimation of necessary information is aimed. In this paper, the joint models of a robot manipulator are identified by RLS algorithm, which is based on a data driven approach from random inputs. A corresponding state observer is designed based on the identified models to estimate the acceleration signals. Experimental studies of identifying the joint models are conducted to demonstrate the proposal.

This paper presents the disturbance torque sensation techniques of control moment gyroscope (CMG) actuators. A torque sensing task without torque sensors can be done by estimating the disturbance. Two torque sensation schemes are presented and their characteristics are compared in the configuration of a disturbance observer. One scheme is based on the linear model identification by the recursive least square (RLS) method. Another sensation scheme is based on the nonlinear model identification with the sigmoidal function. Experimental studies of two torque sensation schemes for CMGs are conducted to compare the performances between two schemes along with different implementation characteristics.

In this paper, a disturbance observer is designed to sense the contact force of a human operator for a control moment gyroscope (CMG). The contact force made by a human is estimated by a disturbance. A disturbance observer is used to estimate the unknown human contact force after the system model identification by a recursive least square (RLS) method. The model-based human contact estimator is designed in a disturbance observer framework to estimate the human contact force as a disturbance. The proposed method is experimentally evaluated by comparing the accuracy of the force estimator and the measured force of a CMG.

Stabilization of the inverse model of the target system is a critical problem in a current disturbance observer (DOB) based control scheme. When the system is identified as a second order system by the recursive least square (RLS) algorithm, the minimum phase (MP) of the model is not guaranteed. This paper addresses a guaranteed minimum phase method of the identified second order model. Jury's test is conducted to check the stability. All-Pass-Filtering (APF) process are conducted for updating prior parameters of RLS to satisfy the minimum phase criteria. To verify the proposal, a single-wheel robot is identified as a second order model by the RLS method with guaranteed stability. Disturbance observer is designed based on the model. Balancing control experiments of a single-wheel robot are conducted.

This paper presents an external disturbance torque sensing technique based on a design of a disturbance observer (DOB). For the more accurate estimation of the system models, two RLS filters are formed a back-to-back cascaded structure to identify both forward and inverse models simultaneously. Monte Carlo-based recursive least squares (RLS) scheme is used for identifying the inverse model of a dynamical system by constructing DOB structure. The proposed torque sensing method is experimentally verified by estimating the external torque of a human operator on the control moment gyroscope (CMG) actuator as a disturbance.