Seiichiro Katsura

Modal System Design of Multirobot Systems by Interaction Mode Control

Motion control technology in an open environment will be more important. Future motion systems should interact with other systems or environments. To adapt to complicated environments and do tasks, a realization of multi-degree-of-freedom motion is necessary for human cooperating motion. This paper proposes a unified control approach for multirobot systems by interaction mode control. The proposed interaction mode control considers only interactions between systems. The interactions are abstracted by using mode quarry matrices. Since the transformed modes are independent of each other, it is possible to design a controller in decoupled modal space. This paper also proposes a novel control index named hybrid ratio. Hybrid ratio is defined as the influence of external acceleration input on the acceleration response of a system. Since it is possible to realize the assigned hybrid ratio in each mode according to the task, the motion command with hybrid ratio is represented as task code. Thus, the interaction mode control is able to be treated as task kinematics. The proposed interaction mode control is applied for grasping motion by multirobot systems. The numerical and experimental results show the viability of the proposed method

Transmission of Force Sensation by Environment Quarrier Based on Multilateral Control

In recent years, realization of a haptic system is desired strongly in the fields of medical treatment and experts skill acquisition. The bandwidth of force sensing and friction compensation are very important problems for reproduction of vivid force sensation. In this paper, an environment quarrier is proposed for bilateral teleoperation instead of force sensors. The environment quarrier is a novel force sensing method which consists of a twin robot system. Two same types of robots are required and they are controlled in the same position, velocity and acceleration by bilateral acceleration control based on a disturbance observer. One robot is in contact motion and the other is unconstrained. The purity of external force is obtained by subtracting the disturbance torque in the unconstrained robot from the constrained one. The environment quarrier can observe the external force with high bandwidth and friction compensation. In order to implement the environment quarrier to a bilateral control system, four robots are required. In this paper, the idea of multilateral control is introduced for attainment of simultaneity. Furthermore, this paper shows that the controller design of the multilateral control in the modal space. The experimental results showed the viability of the proposed method.

Absolute Stabilization of Multimass Resonant System by Phase-Lead Compensator Based on Disturbance Observer

Vibration suppression and attainment of robustness in motion control systems is a big problem in industry applications. To address this issue, several control methods to suppress the vibration have been developed. However, in the conventional vibration control systems, much of the research has not considered the higher order of resonant frequencies. This paper proposes a novel vibration control of a multimass resonant system based on the phase-lead compensator. It also clarifies the influence of the parameter variation of a disturbance observer on acceleration control system. The effect of phase-lead compensation on the acceleration reference is attained by setting a higher nominal inertia value than the actual one. The phase-lead compensator can stabilize all resonant poles of the multimass resonant system. Since the proposed phase-lead compensation system is based on the disturbance observer technique, it can realize suppression of vibration and robustness in motion systems. The experimental results show viability of the proposed method.

Transmission of force sensation by environment quarrier based on multilateral control

In recent years, realization of a haptic system has been strongly desired in the fields of medical treatment and experts skill acquisition. The bandwidth of force sensing and friction compensation are very important problems for reproduction of vivid force sensation. In this paper, an environment quarrier is proposed for bilateral teleoperation instead of force sensors. The environment quarrier is a novel force-sensing method that consists of a twin robot system. Two of the same type of robot are required and they are controlled in the same position, velocity, and acceleration by bilateral acceleration control based on a disturbance observer. One robot is in contact motion and the other is unconstrained. The purity of external force is obtained by subtracting the disturbance torque in the unconstrained robot from the constrained one. The environment quarrier can observe the external force with high bandwidth and friction compensation. In this paper, the idea of multilateral control is introduced for attainment of simultaneity. Furthermore, this paper shows the controller design of the multilateral control in the modal space. The experimental results show the viability of the proposed method

Sensorless interaction force control based on modal space design for twin belt-driven system

This paper proposes a novel sensorless force control algorithm for the belt-driven DD (direct drive) motor servomechanism. The proposed control is obtained by using the disturbance observer combined with modal space design. The two same motors are required and connected by belt-driven mechanism. Each motor has the same characteristics of the friction model and the vibration phenomenon. Therefore, it is easy for the proposed system to compensate these nonlinear effects. The sensorless interaction force control is designed by dual disturbance observer structure. A robust control system is obtained by applying the inner disturbance observer loop in order to cancel out any disturbance torque on the motor side. The outer disturbance observer combined with modal space design is applied to control both belt tension and interaction force of human. The common mode is utilized for control of vibration suppression and belt tension. The other mode is differential mode, which is a friction-free coordinates and useful for control interaction force of human. By using disturbance observer based on modal space design, it is possible to obtain the purity of external force with wide bandwidth. A validation experiment has been performed on a training system. The experimental results point out that the proposed system has a good realization of interaction force between human and the training system.

Bilateral Teleoperation with Different Configurations using Interaction Mode Control

The paper realizes a bilateral teleoperation system considering different configurations. The haptic devices used in this paper are based on three master systems and one slave system. Each master system has one degree of freedom (DOF); and the slave system has three DOF. The conventional coordinate transformation with respect to the Cartesian coordinate system is not always suitable for dexterous tasks including grasping motion. The paper introduces a bilateral teleoperation with spatial mode transformation, which is corresponding to humans task motions. The spatial modes are abstracted by using an interaction mode control. The interaction mode control decomposes the bilateral teleoperation system into three decoupled modes; translational, rotating, and grasping motions. Thus the problems for motion integration of bilateral teleoperation system with different configurations are solved to design each bilateral controller with respect to the spatial mode coordinate system. Furthermore, the proposed system is designed based on acceleration control to realize both the force servoing and the position regulator for the law of action and reaction in remote environment simultaneously. As a result, a complicated task for the slave system is easily realized by three master systems with vivid force feedback. The experimental results show viability of the proposed method.

Advanced motion control by multi-sensor based disturbance observer

Motion control has been widely used in industry applications. One of the key technologies of motion control is a disturbance observer, which quarries a disturbance torque of a motion system and realizes a robust acceleration control. The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems begin to spread in the society and they are required to have ability to contact with unknown environment. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration response by the second order derivative of position response, the bandwidth is limited due to the derivative noise. This paper proposes a novel structure of a disturbance observer. The proposed disturbance observer uses an acceleration sensor for enlargement of bandwidth. Generally, the bandwidth of an acceleration sensor is from 1 Hz to more than 1 kHz. To cover DC range, the conventional position sensor based disturbance observer is integrated. Thus, the performance of the proposed multi-sensor based disturbance observer (MSDO) is superior to the conventional one. The MSDO is applied to position control (infinity stiffness) and force control (zero stiffness). The numerical and experimental results show viability of the proposed method

Haptic recognition and mapping of driving road environment by haptograph

Recently, human cooperative robots are desired in an aging society. In particular, recognition performance of environment is the most important. Visual and/or auditory sensors are used to recognize the environment; however, they are not able to recognize contact information. Tactile and/or haptic information is very important for action in unknown environment. The paper gives the haptic sensation to a robot. Furthermore, the obtained haptic information is visualized by haptograph. The haptograph is useful for haptic mapping of environment and trajectory planning for a mobile robot. The experimental results show the viability of the proposed method.

Bilateral Force Feedback Control Based on Wideband Acceleration Control

Real-world haptics is the key technology for future human support engineering. Because it is able to realize a bilateral recognition between humans action and real environment and transmit the recognized information through human sensations. From the point of view, a future robot should act as the physical agent. Transmission performance of the environmental information to human depends on transparency of a physical agent. The transparency includes spatial and temporal characteristics. Higher spatial transparency transmits much environmental modes. On the contrary, higher temporal transparency transmits wide frequency bandwidth. To improve the transparency, the paper proposes wideband acceleration control for bilateral force feedback control. Since the conventional acceleration control obtains the acceleration information by the second-order derivative of a position response, its bandwidth is limited due to the derivative noise. To enlarge the bandwidth of an acceleration control, the paper proposes a position-acceleration integrated disturbance observer (PAIDO). Since an acceleration sensor is implemented in PAIDO, the bandwidth of the acceleration control based on PAIDO is able to outstrip the one of humans tactile sensation. As a result, vivid tactile sensation is possible in the experimental haptic device. The experimental results show the viability of the proposed method.

High Precision Force Control by Multi-Sensor based Disturbance Observer

Motion control has been widely used in industry applications. One of the key technologies of motion control is a disturbance observer, which estimates a disturbance torque of a motion system and realizes a robust acceleration control. The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems begin to spread in the society and they are required to have ability to contact with unknown environment. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration information by the second order derivative of position response, the bandwidth is limited due to the derivative noise. This paper proposes a novel structure of a disturbance observer. An acceleration sensor is implemented to enlarge the bandwidth in the proposed multi-sensor based disturbance observer (MSDO). Thus, control performance of the MSDO is superior to the conventional one. In this paper, the MSDO is applied to force control and the viability of the proposed method is confirmed by fast Fourier transformation (FFT) analyses