Various actuators have been developed to improve the performance of cooperative robots. Multi-degree-of-freedom (multi-DOF) electromagnetic actuators can rotate multi-DOF by a direct drive and can contribute to system miniaturization and higher precision. However, the biggest challenge is to increase the output because the torque cannot be amplified using a reduction gear. To solve this problem, this paper focuses on a hybrid actuation with a pneumatic actuator, which has a large output density. In this study, we propose a two-DOF pneumatic-electromagnetic hybrid actuator that integrates a bellows pneumatic actuator and a two-DOF electromagnetic actuator. First, the concept, design, and operating principle are presented. Next, the torque control method, dynamic model, and attitude control system are shown. In the torque analysis, the maximum torque of the proposed actuator is four times larger compared with a conventional two-DOF electromagnetic actuator of the same size. The dynamic simulation results show that attitude control is possible with hybrid actuation. Based on the results, a hybrid multi-DOF actuator using multiple drive sources is proposed for the first time.

A triaxial active control magnetic bearing with an axially asymmetric structure has been developed for a high-temperature turbomachinery. Since this magnetic bearing has a support force interference, disturbance suppression was not possible. A nonlinear compensator has already been proposed to solve this problem. However, the disturbance suppression performance is insufficient. Therefore, this paper proposes a switching type disturbance suppression control system that estimates a disturbance from the states and switches the controller characteristics based on an estimated disturbance. This model improves the disturbance observer performance of the already proposed a variable structure type nonlinear control system. First, the characteristics of the proposed model are presented, followed by the disturbance estimation performance of the proposed model. Next, the disturbance suppression performance of the proposed model and a conventional compensator is compared. The results verify the superiority of the proposed model over conventional compensators.

Magnetic lead screw (MLS) is a feed screw that allows non-contact power transmission. The MLSs have some advantages such as reduction of particle emission and improving positioning accuracy. However, conventional MLSs need a supporting mechanism using linear guides or slide bearings. They deteriorate the advantages of MLSs because of friction. In order to solve this problem, we propose a magnetically levitated lead screw (MLLS) for complete non-contact transmission. The proposed magnetic structure and operating principle are verified through a three-dimensional finite element method. The suspension force, thrust, and torque characteristics are investigated, and the effectiveness of the MLLS are clarified.

Analytical calculations of electrical machines are expeditious tools for the design and the analysis of their performance. In contrast with conventional electrical machines such as a brushless DC motor, induction and synchronous machines, a magnetic geared motor (MGM) is operated using space harmonics of magnetic flux in the air gap due to the magnetomotive force of the permanent magnet on the high speed rotor and stator, and the air gap permeance of the low speed rotor and the stator teeth. This paper describes the operational principle of the MGM and the comparison of the air gap magnetic flux density between an analytical calculation and the finite element analysis.

We proposed a linear oscillatory actuator for active vibration damping, which converts rotational motion into linear motion using a DC motor. In this study, we verified the vibration damping performance of the proposed actuator through simulations by coupling FEM with MATLAB/Simulink and experiments on a prototype.

We have been studying small sized direct-drive electromagnetic linear actuators and their control method. These actuators were able to emulate the viscoelastic characteristics of the human muscle by PD position control to respond to external forces flexibly. However, their thrust force was not enough in order to apply to legs and shoulders of robots. In this paper, we present a novel small cylindrical linear vernier motor for artificial muscle of humanoid robots. First, the structure and operating principle of the proposed linear vernier motor are described. Then, the thrust and detent force of the motor are shown by 2D finite element analysis and measurement on a prototype. As the result, the validity of the simulation is discussed. Finally, the effect of the position controller with the disturbance observer on reduction of detent force and deviation between target and actual mover position is clarified.

The compliance of muscles with external forces and the structural stability given by biarticular muscles are important features of animals to realize dynamic whole body motions such as running and hopping in various environments. For this reason, we have been studying an electromagnetic linear actuator. This actuator can emulate the behavior of a human muscle such as the spring-damper characteristics by quick control of the output force (i.e. impedance control) and it is expected to be used as an artificial muscle. In this paper, we develop a monopedal robot possessing bi- and mono-articular muscles implemented by linear actuators. Thanks to the biarticular muscle, the bouncing direction of the robot can be controlled by changing the stiffness ellipse at the endpoint (i.e. foot) of the robot. We confirm that the bouncing direction of the robot can be controlled and hopping can be achieved by changing the stiffness ellipse.

In order to realize androids and humanoids that have very humanlike mechanisms and movements, the development of new linear actuators is necessary. In the development of the actuators, we have found a structure of the linear actuator that is more powerful and quick through iterative simulations based on the 3D finite element method and developed the prototype. This paper reports the structure and various simulations of the new linear actuator. We consider this new actuator will be one of the important components of robots, such as androids and humanoids.