Katsuyoshi Tsujita

Adaptive gait pattern control of a quadruped locomotion robot

The authors have proposed a control system of a quadruped locomotion robot by using nonlinear oscillators. It is composed of a leg motion controller and a gait pattern controller. The leg motion controller drives the actuators of the legs by using local feedback control. The gait pattern controller involves nonlinear oscillators with mutual interactions. In the paper, capability of adaptation of the proposed control system to variance of the environment is verified through numerical simulations and hardware experiments. With the input signals from the touch sensors at the tips of the legs, the nonlinear oscillators tune the phase differences among them through mutual entertainments. As a result, a gait pattern corresponding to the states of the system or to the properties of the environment emerges. The robot changes its gait pattern adaptively to variance of the environment and establishes a stable locomotion while suppressing the energy consumption.

Locomotion control of a biped locomotion robot using nonlinear oscillators

This paper proposes the locomotion control system for a biped locomotion robot. The propose control system is composed of motion generator system and motion control system. Motion generator system is composed of nonlinear oscillators, which generate the commanded trajectories of the joints as functions of phases of oscillators. Motion control system is composed of motors with controllers installed at joints, which control motions of joints. The oscillators tune the phases through the mutual interactions and the feedback signals from the touch sensors at the tips of the legs. As a result, the robot with the controller walks stably by changing its period of locomotion in a changing environment. The performance of the proposed control system is verified by numerical simulations and experiments.

Gait transition by tuning muscle tones using pneumatic actuators in quadruped locomotion

The development of an oscillator controller for a quadruped robot with antagonistic pairs of pneumatic actuators is reported. Periodic motions of the legs switch between the swinging and supporting stages based on the phase of the oscillators. The oscillators receive touch sensor signals at the end of the legs as feedback when the leg touches the ground and compose a steady limit cycle of the total periodic dynamics of quadruped locomotion. And also muscle tone is adaptively controlled according to the dynamic state of the main body. This system can generate gait transition from one to another by changing locomotion speed and muscle tone. The effectiveness and performance of the proposed controller were evaluated with numerical simulations and experiments with the hardware.

Motion control of a two-wheeled mobile robot

The design of the controller of a two-wheeled mobile robot is usually based on a kinematical model. The kinematical model is derived under the assumption that the wheels do not skid or float. However, in the real world, wheels may skid on the ground or float away from the ground due to the rotational motion of the body. This paper analyzes the effects of the skid and the float on the robot with a controller designed based on the kinematical model—by the use of the Lyapunov control method. Numerical simulations are carried out based on the dynamic model including the translational and rotational motion of the body, and then experiments are performed using a hardware model.

Turning control of a biped locomotion robot using nonlinear oscillators

In our previous work, we developed a locomotion control system of a biped robot which is composed of nonlinear oscillators and realized a stable straight walk of the biped robot against the changes of the environments. Then, we revealed that the adaptability to the changes of the environments is realized as the straight walk results in the change of the period of the motions of the legs. In this paper, we realize a turning walk of the biped robot by using the developed locomotion control system. First, we provide analysis of the turning behavior of the biped robot and reveal that, in this case, the turning behavior leads to the change of the duty ratios of the legs. Moreover, we realize the task that the robot pursues a target on the floor moving along a corner and it demonstrates that the robot can turn a corner successfully in the real world.

Oscillator-Controlled Bipedal Walk with Pneumatic Actuators

The development of an oscillator controller for a bipedal robot with antagonistic pairs of pneumatic actuators is reported. Periodic motions of the legs switch between the swinging and supporting stages based on the phase of the oscillators. The oscillators receive touch sensor signals at the end of the legs as feedback when the leg touches the ground and compose a steady limit cycle of the total periodic dynamics of bipedal locomotion. The effectiveness and performance of the proposed controller were evaluated with numerical simulations and experiments with the hardware.

Dynamic turning control of a quadruped locomotion robot using oscillators

We propose a dynamic turning control system for a quadruped robot that uses non-linear oscillators. It is composed of a spontaneous locomotion controller and voluntary motion controller. We verified the mechanical capabilities of the dynamic turning motion of the proposed control system through numerical simulations and hardware experiments. Various turning speeds and orientations made the motion of the robot asymmetrical in terms of the duty ratio, stride and center of pressure. The proposed controller actively and adaptively controlled redundant degrees of freedom to cancel out dynamic asymmetry, and established stable turning motion at various locomotion speeds and turning orientations.

Attitude Control of a Spacecraft with Two Reaction Wheels

This paper deals with the attitude control of a rigid spacecraft with two reaction wheels. First, we derive a discontinuous state feedback law based on Lyapunov control. The control input is obtained by multiplying the gradient vector of the Lyapunov function by a matrix that is composed of a symmetric matrix and an asymmetric one. Under this method, when the angular momentum of the system is zero, the desired point is the only stable equilibrium point of the controlled system. Next, we investigate the behavior of the controlled system when the angular momentum of the system is not zero but small. In this case, the system converges to either a limit cycle or an equilibrium point which is not the desired point however, in both cases, the error in attitude remains small.

Development of human-machine interface in disaster-purposed search robot systems that serve as surrogates for human

This research project, as a part of special project for earthquake disaster mitigation in urban areas initiated by the MEXT, aims to extend the existing robotics and human interface technologies and to establish a novel human-machine interacting structure to enable effective use of semi-autonomous robots in place of humans for searching survivors from rubble under human remote instructions. Collaboration and coordination of the human and robot intelligence and skills are to be developed from both hardware and software viewpoints to make the results of this project contribute to improvement of the search technology, an important issue in the urban robot-assisted search and rescue activities. Research efforts and results are described in this paper.

Locomotion control of a multi-legged locomotion robot using oscillators

This paper proposes the locomotion control system for a multi-legged locomotion robot. The proposed control system is composed of leg motion controllers and a gait pattern controller. The leg motion controllers drive the actuators of the legs by using local feedback control. The gait pattern controller is composed of nonlinear oscillators. The oscillators tune the phases through the mutual interactions and the feedback signals from the touch sensors at the tips of the legs. Various gait patterns emerge through the mutual entrainment of these oscillators. As a result, the robot with the controller walks stably by changing its gait patterns in a wide range of locomotion speed. Moreover, it continues to walk even if a part of leg controller breaks down. The performance of the proposed control system is verified by numerical simulations.