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This paper presents research on a new vibration suppression method for stepping motors. A new compensation method for stepping motor controllers, which cancels out the cogging torque without using any additional electronic devices and mechanical parts such as angler position sensors, is proposed. This paper is organized as follows. First, a transfer function based on the feed-forward compensation that describes motions and electric circuits for tow-phase hybrid stepping motor is derived. Next, experiments for the motor drive controller conducted to evaluate the rotor vibration are presented. Then, computer simulation on vibrations for a print-head carriage system driven by a stepping motor is described to verify effectiveness of our proposed method. Finally, it is concluded that experimental and simulation results show that our proposed method is effective in the vibration suppression.

When positive feedback of joint torques is applied to motion control of robot arms, the nonlinear dynamic couplings between links are canceled and a servo system with high stiffness is obtained.The problems which arise due to joint flexibility in the robot motion control based on joint torque positive feedback are discussed in this paper.We investigate the effects of joint flexibility by numerical and experimental studies on a one-link arm with a harmonic drive.It is shown that the joint flexibility destabilizes the control system with joint torque positive feedback.A low-pass filter is used in the torque feedback loop to improve the oscillation characteristics of the control scheme.

We have proposed the practical torque sensor which utilizes elasticity of harmonic drives. The sensing technique provides joint torque sensing without reducing stiffness of the robot and changing the mechanical structure of the joints. I n this paper, we examine experimentally the characteristics of joint torque control using this torque sensor. Three types of torque control laws are implemented with a one-link arm to find a control method which provides excellent friction reduction and dynamic response in joint torque. The experimental results of joint torque control show that the torque sensor is very useful to compensate the nonlinear friction. Furthermore the torque control is effective to improve the accuracy of the motion control at low velocity and to suppress the vibration caused b y the joint fEexib ility .