Kyosuke Ono

Self-Excited Walking of a Biped Mechanism With Feet

In this paper we present a theoretical and experimental study of the self-excited walking of a biped mechanism with knees and feet on level ground. This biped mechanism possesses a single motor at the hip joint and active lock mechanisms at both knee joints. We first show that the self-excitation control enables the three-degrees-of-freedom planar biped model with feet to walk on level ground, and that a stable walking locomotion is possible over a wide range of feedback gain and a foot radius of up to 0.3 m. Subsequently, we describe the manufactured biped Robot 2 which is similar to the analytical model and we show that the biped robot can perform natural dynamic walking on a level floor. It is also shown that the simulated results agree well with the experimental results. We further describe the wireless-controlled biped Robot 3, which can walk on a level floor carrying batteries and electronic circuits inside the thighs.

Self-Excited Walking of a Biped Mechanism

The authors studied the self-excited walking of a four-link biped mechanism that possesses an actuated hip joint and passive knee joints with stoppers. They showed that the self-excitation control enables the three-degree-of-freedom planar biped model to walk on level ground by numerical simulation. From the parameter study, it was found that stable walking locomotion is possible over a wide range of feedback gain and link parameter values and that the walking period is almost independent of the feedback gain. Various characteristics of the self-excited walking of a biped mechanism were examined in relation to leg length, and length and mass ratios of the shank. Next, a biped mechanism was manufactured similar to the analytical model. After parameter modification, the authors demonstrated that the biped robot can perform natural dynamic walking on a plane with a 0.8 degree inclination. The simulated results also agree with the experimental walking locomotion.

Self-excitation control for biped walking mechanism

This paper presents the self-excited walking of a four-link biped walking mechanism which possesses an actuated hip joint, passive knee joints and a curved feet. Instead of gravity potential energy, the natural walking motion of the four-link biped mechanism is self-excited by the hip joint torque which is proportional to the angle of the swing shank. In this paper, we show that this self-excitation control enables the 3-DOF planar biped model to walk on level ground by numerical simulation. From the parameter study of the feedback gain, we found that stable walking motion was possible over the wide range of this parameters, and walking velocity and periods were not so much affected. It was confirmed that the properties of this self-exciting walking, such as walking velocity and duration, were changed by the structural parameters of the walking model.

Control of giant swing motion of a two-link horizontal bar gymnastic robot

We investigated a control method to realize the three different types of free giant swing motions produced by a two-link horizontal bar gymnastic robot. By evaluating the eigenvalues of the transitional error matrix on the Poincare plane, it was found that the stable giant swing motions could be obtained by a proposed configuration control, in which the actuated joint torque is controlled such that the measured state variables follow the reference configuration with respect to the angular position of the passive joint. We also demonstrated that the two types of stable giant swing motions could be accomplished by the configuration method.

Fundamental Characteristics of a New Variable Torque Clutch With Skewed Rollers

In this paper, a new type of a clutch by the name of the variable torque clutch with skewed rollers is first introduced and second investigated both theoretically and experimentally. It is comprised of an inner and an outer race that are each in spatial line contact with the crossed axis cylindrical rollers. Torque transmission is delivered by a slipping induced between the rollers and the races due to skewing the rollers. The equations of the race surfaces are derived and the geometrical properties are analyzed. Based on the kinematic analysis, a roller-wedge model is proposed for this clutch in order to visualize the motion at the tangency of the rollers and the races, By assuming the linear distribution of the contact force along the spatial contact line, the transmitted torque capacity and kinematic characteristics can be evaluated properly from the solution of a set of nonlinear equilibrium equations. Several prototypes of this clutch are manufactured and measured to show the validity of this design idea and the theoretical results. The computational results are found to coincide with the experimental data. In addition, the influences of the design parameters on the fundamental characteristics are discussed in detail.

Accuracy Analysis of Optimal Trajectory Planning Methods Based on Function Approximation for a Four-DOF Biped Walking Model

Based on an introduced optimal trajectory planning method, this paper mainly deals with the accuracy analysis during the function approximation process of the optimal trajectory planning method The basis functions are composed of Hermit polynomials and Founer series to improve the approximation accuracy Since the approximation accuracy is affected by the given orders of each basis function, the accuracy of the optimal solution is examined by changing the combinations of the orders of Hermit polynomials and Fourier series as the approximation basis functions As a result, it is found that the proper approximation basis functions are the 5th order Hermit polynomials and the 7th-10th order of Fourier series

Surface texture parameters of perpendicular recording magnetic disks

This paper presents measured surface texture parameter values critical for evaluating the mechanical reliability of the head-disk interface in perpendicular magnetic recording with a small clearance of less than 1 nm. It was found that mean asperity height is ~0.5 nm and asperity density is ~5000 μm-2. The asperity radius of curvature has an anisotropic nature but its averaged value is ~20 nm. The radius of highest asperity group related to asperity contact appears to be close to ~10 nm.

Passive/active unified dynamic walking for biped locomotion

In order to implement walking efficiency and environmental adapting ability to a biped locomotion, it is required to combine passive dynamic walking and active one. In this paper, a passive/active unified dynamic walking for biped locomotion was proposed. Firstly, a passive/active unified actuator that has a torque detector and is actively controlled by zero torque feedback control was proposed and developed. Next, a free moving joint used in passive motion was implemented analytically and experimentally to a one-joint one-link and a two-joint two-link mechanism with a reduction gear using this developed actuator. Furthermore, in order to apply it to a biped walking robot, a passive/active unified dynamic walking control algorithm was proposed. Moreover, 2-D passive/active unified dynamic walking of a three-joint four-link biped robot was implemented experimentally by applying self-excited control to the passive walking phase of the swing leg. Finally, we showed the energy-efficient walking using the proposed method by comparing Specific Cost of other types of dynamic walking, and mentioned its adaptability to disturbances and unknown environment.

Control of giant swing motion of a two-link underactuated horizontal bar robot

We investigated a control method to realize the three types of free giant swing motions of a two-link horizontal bar robot. By evaluating eigenvalues of the transitional error matrix on the Poincare plane, it was found that the stable giant swing motions can be obtained by configuration control, in which the actuated joint torque is controlled such that the measured state variables follow the reference configuration with respect to the angular position of the passive joint. We also demonstrated that the stable giant swing motions of type B and C could be realized by the configuration method.

Analysis of dynamic characteristics for cylindrical journal bearing based on average flow theory.

As a preliminary study on elastic cylindrical journal bearing, this paper presents an analytical method and the calculated results of the static and dynamic characteristics of a rigid cylindrical journal bearing, based on an average flow model theory. By using a modified law of the equivalent lubricant density and viscosity in the negative pressure region, reasonable static pressure distributions with small negative pressure or zero pressure can be obtained. Dynamic pressure distributions, produced by journal velocity, are consistent with those in infinitely long journal bearing theory, proposed by the author in the previous paper. Elastic and damping coefficients are qualitatively equal to the prevailing numerical results. It is also found that the unstable threshold speed and whirl frequency of a rigid rotor and bearing system are in good agreement with those in infinitely long journal bearing theory, described above.