The purpose of this paper is to propose a new type of a kinetic chained walking robot capable of walking with only a single actuator, and is to design its trajectory tracking control system. Legged robots are able to move across irregular terrains, however, have an issue on energy efficiency compared with other morphology. A bio-inspired approach often provides effective solutions, for example, a lizard is able to mainly walk by utilizing only twisting its waist. To mimic this characteristic by robotics, a robot consisting of four-bar linkage mechanism is proposed. This idea improves simplification of its locomotion analysis. In this paper, two important kinematics characteristics are analyzed in order to propose locomotion ability and effectiveness of the robot. In particular, a turning angle and a stride distance are analysed. After that, a trajectory tracking control system is designed based on the PID control low. Ideas for the control system design in this paper are both to decide an bias of an input angle function as a input of the system and to set a control period on half period of the input angle function. Finally, effectiveness of the designed control system is verified via numerical simulations. A straight line and a circle trajectory are adopted for the verification. As the results, it is shown that the designed trajectory tracking control system is capable of tracking two different trajectory. In addition, it is also shown that the designed trajectory tracking control system satisfies the kinematics analysis results from the side of view of the kinematic of the robot.

Muscle-tissue of earthworms is an excellent actuator due to its membranous structure, strong force, short response time, and controllability. In this paper, we first investigated the output force, control property including stimulation voltage, stimulation frequency, and duty. Secondly, we designed, fabricated, and demonstrated an atmospheric-operable walking robot by using a muscle-tissue of earthworms. The maximum walking speed was about 0.56 mm/s, which is about 2 times faster than other types of bio actuated walker. The maximum atmospheric driven time was over 45 minutes. These demonstrated results indicated that the muscle-tissue of earthworm has a high potential for using as a biological micro bio-actuator for multiple purposes.

This paper proposes a linear power assist unit to be simply designed by using an add-on end-effector and gives a controller design for the unit explicitly taking into consideration mechanical impedances of both a human operator and environment. The proposed end-effector transmits assisting force to the environment via a pair of assisting springs, and the displacement of the assisting springs is controlled to generate a desirable power assisting according to the force applied by the operator. In the proposed system, the assist gain, i.e., the ratio of the sum of the human-applied force and the assisting force to the human-applied force, can be online changed so as to easily adjust a stress loading, and it could be helpful in rehabilitations to tune the load depending on the degree of recovery. A prototype of the proposed power assist unit has been developed and was evaluated from viewpoints of both the time and frequency domains. Experimental results showed that the prototype has robustly worked well against perturbations of the environment, keeping the power assist control bandwidth about 1 to 3 Hz, and the validity of the variable assist gain control has also confirmed.

This paper proposes a two stage actuator system that consists of a coarse actuator driven by a ball screw with an AC motor (the first stage) and a fine actuator driven by a voice coil motor (the second stage). The proposed actuators are applied to make a wide-bandwidth bilateral control system. The first stage has a wide moving range with a narrow control bandwidth, and the second stage has a narrow moving range with a wide control bandwidth. In the proposed method, by consolidate these two inexpensive actuators based on a control design to separate bandwidth, a wide bandwidth bilateral control system can be constructed. Simulation results show that a higher transparency, i.e., better force and position responses between a master and slave, is achieved by using the proposed system compared with a narrow-bandwidth case using a single ball screw system. Furthermore, a prototype of the two stage actuator has been developed and basic performance was evaluated by experiment. Experimental results showed that a light mechanical impedance with a mass of 10 g and damping of 1.6 N/(m/s) that is an important factor to establish good haptic devices was successfully implemented.

In this paper, we propose a control method to swing up and stabilize a double Furuta pendulums (DFP).The DFP is a rotational type inverted pendulum system that has a base-link and two pendulums of different length at the both ends of the base-link. The proposed method consists of three controllers for the DFP, i.e., a swinging up controller for a long pendulum, a controller to keep a long pendulum at the upright position and to swing up a short pendulum simultaneously, and a stabilization controller for both pendulums at the upright position. Since the second controller has two objectives, we use safe manual control proposed by Astrom and Akesson. This paper proposes a novel application of the safe manual control. Swinging up and stabilization of the DFP was successfully achieved by appropriately switching three controllers. The effectiveness of the proposed method was verified by simulation and experiment.

Bucky gel actuator is a novel electro-active polymer (EAP), which is a low-voltage driven dry soft actuator. In addition, the bucky gel device generates electromotive force when bending, and then it also can be used as a sensor. Its device has a bimorph structure with polymer-supported bucky gel electrodes and a polymer-supported ionic gel electrolyte. It can be fabricated by layer-by-layer casting, to form any shape easily. In this paper, we demonstrate an automatic fabrication method of the bucky gel devices based on a printing method. By using a dispensing machine, we construct the printing system, and manual forming process is replaced with automatic printing. We investigate the printing of complicated shapes and 3D electrode pattern through experiments.

This paper is concerned with the development of the capsule robot (Capsubot) which can move with no external parts. It is easy to be constructed in small scale and maybe can be used for medical uses such as the endoscope since the Capsubot moves bidirectionally. The Capsubot could move by exerting friction force through movement of inside mass. This paper shows theoretical analysis and experimental verification of the locomotion for the Capsubot. In the experiment, the motion of inner mass is generated by coils and a magnet. Displacement of the Capsubot is measured by laser sensor and also position of the inside mass is measured. Using the developed test system, the motion of the developed Capsubot is experimentally compared with the one of the theoretical model.

Bucky gel actuator is a novel electro-active polymer (EAP), which is a low-voltage driven dry soft actuator. Its device has a bimorph structure with polymer-supported bucky gel electrodes and a polymer-supported ionic gel electrolyte. It can be fabricated by layer-by-layer casting, to form any shape easily. In addition, the bucky gel device generates electromotive force when bending, and then it also can be used as a sensor. Since sensor and actuator functions exist in a same device, flexible and miniature integrated actuator-sensor systems for soft robotics can be constructed easily. In this study, we conduct some experiments to verify the possibility of the bucky gel actuator/sensor. Feedback controls of the actuator are demonstrated and the characteristics of the sensor are investigated. By utilizing both functions of the actuator and the sensor, feedback control based on the sensor signal is demonstrated.

We constructed a snake-like swimming robot using IPMC actuator, and verified swimming motion based on numerical simulation and experiments. In applying periodic inputs with appropriate frequency and phase shift, the snake-like robot is capable of smooth propulsion. It is known that IPMC has a sensor function that IPMC films generate electromotive voltage when bending or being deformed. By using the sensor function into the snake-like robot, it is considered that autonomous propulsive motion can be realized by feedback of the sensor signal. In this paper, we consider the autonomous locomotion of the snakelike swimming robot with IPMC actuator/sensor, and verify the realization of swimming motion by feedback of the sensor signal. Furthermore, the efficiency of the autonomous locomotion is investigated

We are studying about robotic application of ionic polymer-metal composite (IPMC). The characteristics of IPMC highly depend on the type of counter-ions, and it is considered that the performance of the actuators can be improved by combining the actuators with several types of counter-ions and applying an integrated control. IPMC has also a sensor function, as the IPMC film generates electromotive force when it is deformed. It has possibility to be integrated into IPMC actuator with soft actuation. In this paper, we consider an integrated design of IPMC actuator/sensor, and investigate a control of the combined IPMC actuators using Hinfincontrol and the construction of IPMC sensor system

Ionic polymer metal composite (IPMC) is one of the most promising EAF actuators for applications, and slave good property of response and durability. The characteristics of IPMC materials depend on a type of counter ion. In applying to mechanical systems such as a robot, there exist possibilities to change the properties of the dynamics by changing the counter ions according to environment or purpose adequately. In this paper, we consider swimming of a snake-like robot with IPMC actuator, and demonstrate a smooth swimming motion. Then, we also verify the doping effects by experiments.

This paper proposes novel energy-based gait generation and control methods for biped robots based on an analysis of passive dynamic walking. First, we discuss the essence of dynamic walking using a passive walker on a gentle slope from the mechanical energy point of view. Second, we propose a simple and effective gait-generation method, which imitates the energy behavior in every walking cycle considering the zero-moment point condition and other factors of the active walker. The control strategy is formed by taking into account the features of mechanical energy dissipation and restoration. Following the proposed method, the robot can exhibit a natural and reasonable walk on a level ground without any gait planning and design in advance. The effectiveness of the method is examined through numerical simulations and experiments.

This paper proposes a novel energy-based control law for biped robots based on an analysis of passive dynamic walking. Firstly we discuss the essence of dynamic walking using a passive walker on a gentle slope. In the second, we propose a simple and effective control law which imitates the energy behavior in every cycle considering the ZMP condition and other factors of the active walker. The control strategy is formed by the feature of mechanical energy dissipation and restoration. By the effect of the proposed method, the robot can exhibit natural and reasonable walk on a level ground without any gait design in advance. The validity of the proposed method is examined by numerical simulations and experiments.

In our previous works (2000), we have proposed "virtual passive dynamic walking" utilizing modified gravity condition with virtual gravity field. The virtual passive walking motion critically depends on the physical parameters and the steady walking pattern is not easily obtained without suitable physical parameters. In this paper we propose a more generalized method of virtual passive walk and a virtual passivity mimicking control law. With the effect of the control laws, we can generate the steady walking pattern even if the physical parameters are not suitable. We call the walking pattern generated by the control methods as "extended virtual passive dynamic walking". The validity of the proposed method is examined by numerical simulations and tested by a prototype experimental machine.

In our previous works (2000), we proposed some system augmentation methods for dynamic bipedal walking in order to realize variable walking patterns in real-time, however, the robust performance of the methods were discussed. Based on the observation we propose a new coupling control law considering the flywheel effect for robustness. In this paper the validity of the methods is analyzed and investigated by numerical simulations and experiments.