The disturbance observer (DOB) has been widely utilized for high-precision and high-speed motion control applications. In this note, we suggest the robustness measure of the DOB as a criterion to design the robust DOB systems. Also, we suggest its design guidelines especially for second-order systems. Experimental results for an optical disk drive system show the validity of design guidelines.

This paper proposes the walking pattern generation method, the kinematic resolution method of center of mass (CoM) Jacobian with embedded motions, and the design method of posture/walking controller for humanoid robots. First, the walking pattern is generated using the simplified model for bipedal robot. Second, the kinematic resolution of CoM Jacobian with embedded motions makes a humanoid robot balanced automatically during movement of all other limbs. Actually, it offers an ability of whole body coordination to humanoid robot. Third, the posture/walking controller is completed by adding the CoM controller minus the zero moment point controller to the suggested kinematic resolution method. We prove that the proposed posture/walking controller brings the disturbance input-to-state stability for the simplified bipedal walking robot model. Finally, the effectiveness of the suggested posture/walking control method is shown through experiments with regard to the arm dancing and walking of humanoid robot.

This paper presents an electromyographic (EMG)-based continuous control scheme including simple classifier for an electric-powered wheelchair, ultimately for quadriplegics. The proposed scheme utilizes three EMG signals as inputs for the muscle-computer interface. Since zygomaticus major muscles and transversus menti muscle of human face are able to move independently as well as to adjust contractile forces voluntarily, the surface EMG signals on these muscles are utilized for the electric-powered wheelchair control system. To extract the envelopes of the signal waveforms and to reflect the moving average activities, the root-mean-squares (RMS) operation and normalization are subsequently employed as initial signal processing. Then, an activation vector containing three normalized RMS signals is obtained in real time. The activation vector is applied to the simple classifier for finding out the motion command. Both desired linear acceleration and angular velocity are yielded from the linear combinations of the classification result and the magnitude of activation vector. Finally, desired wheel velocities of the wheelchair control system are obtained by using the integration and differential inverse kinematics. The effectiveness of the proposed control scheme is verified through several experiments such as avoiding obstacle cones and navigating long distance by the users.

Surface electromyography (sEMG) sensor is widely used to operate a myoelectric prosthesis and it has been further developed for various applications. In this paper, a multi-channel sEMG knit band sensor is newly suggested to be worn easily by amputee for myoelectric prosthesis. The band sensor was fabricated by knitting the silver-plated conductive yarn for electrodes with the moisture-wicking technical yarn for the comfort, ultimately, to record eight-channel sEMG signals simultaneously. Several experiments were conducted to verify the performance of knit band sensor. The normalized correlation between the developed knitted electrodes and the disposable (Ag/AgCl) electrodes is very high (0.95) at the same muscular area. The average signal-to-noise ratio value of the knitted electrodes (17.91 dB) was higher than that of the disposable electrodes (13.30 dB). For the performances of motion classification, overall classification accuracy of the knitted electrodes (93.2%) was higher than that of the disposable (87.9%). These experimental results have supported that the developed knit band sensor was as effective as the disposable electrodes.

This paper proposes a new actuator system for mobile robot applications. Since the actuator system to be proposed consists of dual-motors and a planetary gear, it is referred to as the dual-motor system using a planetary gear (DuPG) in this paper. The suggested DuPG improves the speed-torque performance by combining two motors with one planetary gear, in which one motor is for high speed and the other for high torque. In other words, it is able to realize a high speed at low torque, and high torque at low speed, as an automatic transmission operates in an automobile. The proposed actuator system is able to extend the speed/torque operation region. Finally, several experimental results are suggested to show a few advantages such as the extended speed/torque operation region and the enhanced energy efficiency.