Kan Yoneda

Development of optical six-axial force sensor and its signal calibration considering nonlinear interference

A six-axial force sensor using the optical measuring technique and its nonlinear calibration method are proposed. The force sensor is based on a unit which has a small light source set face to face with a photosensor of the quarter-splitting type to measure minute displacements in two directions with respect to each other. Three sets of the unit are held by an elastic frame. The sensor, in comparison with the conventional strain-gauge-based device, is more compact, light in weight, low in cost, and accurate. The high accuracy of the sensor comes from the calibration method in which nonlinear interferences of six-axial force are considered. An experimental setup in which the six-axial force sensor could be simultaneously input with plural axial forces was produced, and the proposed calibration method was shown to be valid.<<ETX>>

Feedforward and feedback dynamic trot gait control for a quadruped walking vehicle

To realize dynamically stable walking for a quadruped walking robot, the combination of the trajectory planning of the body and leg position (feedforward control) and the adaptive control using sensory information (feedback control) is indispensable. In this paper, we propose a new body trajectory, the 3D sway compensation trajectory, for a stable trot gait; we show that this trajectory has a lower energy consumption than the conventional sway trajectory that we have proposed. Then, for the adaptive attitude control method during the 2-leg supporting phase, we consider four methods, that is, a) rotation of body along the diagonal line between supporting feet, b) translation of body along the perpendicular line between supporting feet, c) vertical swing motion of recovering legs, and d) horizontal swing motion of recovering legs; we then describe how we verify the stabilization efficiency of each method through computer simulation, stabilization experimentation, and experimenting in walking on rough terrain using the quadruped walking robot, TITAN-VIII.

Design of prismatic quadruped walking vehicle TITAN VI

A quadruped walking vehicle TITAN VI having a new leg mechanism is designed and manufactured. Objectives of design of TITAN VI are to walk on an ordinary staircase of 30 to 40 degrees, to constitute an active platform which assists manipulation in the stationary condition, and to walk at a high speed by using dynamic walk. The new mechanisms introduced in TITAN VI are, (1) prismatic joint leg mechanism which does not interfere with the steps of a staircase, and which performs a cylindrical coordinates motion with good energy efficiency, (2) an articulated body structure having node which copes with a steep staircase, (3) a vertical foot driving system having a dual mode transmission mechanism and the like. The detail of these mechanisms are discussed. The effectiveness of these considerations are verified by the walking experiment using the trial-manufactured TITAN VI. >

Quadruped walking robots at Tokyo Institute of Technology

In this article, the design principle of the leg driving mechanism to minimize energy loss and maximize output power is discussed. We will also introduce the gait control methods implemented in our previous quadruped walking robots. Finally, we will survey most of the prototype models of our quadruped walking robots.

Maneuvering operations of the quadruped walking robot on the slope

On the assumption that a quadruped robot works on a slope, we discuss how to make it prevent tumbling over. The larger the difference becomes between the potential energy of the center of gravity of the initial position and that of the highest position after its rotating, the less the robot tumbles. So this difference can be regarded as stability margin, and a novel gait to obtain largest stability margin is mentioned here. It is an intermittent crawl gait. Its energy stability contour (consisting of equal stability points on the inclined plane) is helpful in the design of standard foot trajectories. An optimal posture on the slope, designed in this way, results in inverse trapezoid shape, which means that upper two legs are located wider than lower two ones. This form worked for the experimental machine, TITAN VII. Furthermore, if the standard trajectory for one direction is combined with another direction trajectory, the quadruped robot can easily switch its proceeding directions, keeping enough stability margin. This sequence is shown.

Dynamic and static fusion gait of a quadruped walking vehicle on a winding path

The authors previously (1989) proposed the concept of dynamic and static fusion gait control and discussed a basic control scheme for the purpose of adaptive selection of these gaits during continuous walking. They extend the concept to walking at variable speeds along a winding path. The motion scheme is discussed on the basis of a generalized trot gait and incorporates stability control based on feedforward and feedback control; trajectory modification is based on the zero moment point concept. The validity of these discussions is verified by walking experiments with quadruped walking vehicles TITAN IV and TITAN VI; e.g., dynamic and static fusion gaits at velocities from zero to 400 mm/sec by TITAN IV, and walk with dynamic stability along a circular winding path at a velocity of 100 mm/sec by TITAN VI. At present, dynamic walk on rugged terrain is not possible, but it may be made possible by introducing feedback control as discussed.<<ETX>>

Fundamental considerations for the design of a planetary rover

Outlines the fundamental considerations for a planetary rover. First, shapes which utilize limitless rotation such as wheels and crawlers, legged shapes, and articulated body shapes were compared, and it was found that the wheel type is currently the optimum for a planetary rover. Next, the authors study specific methods for configuring planetary rovers with one, two, and three wheels, which is a topic that has not been studied much before, and in particular, the authors indicate that it is effective to equip these vehicles with manipulator arms and make joint use of the arm for movement. The authors also study a four-wheel rover, and propose a rhomboid four wheels vehicle arrangement as a mechanism to manifest terrain adaptability comparative to the six wheels vehicle.

Research on a six-legged walking robot with parallel mechanism

A new lightweight six-legged robot is developed which uses a simple mechanism and can move and work with high efficiency. This robot consists of two leg-bases with three legs each and walks by moving each leg-base alternately. These leg-bases are connected to each other through a 6-DOF mechanism. Thus, when the robot stands on three legs, or one leg-base is placed on the ground, the other leg-base can be used as a 6-DOF manipulator or active working platform. The output force, velocity, and movable range of various mechanisms for connecting the two leg-bases were compared and the results showed that good performance could be achieved with a serial-parallel hybrid mechanism consisting of three 6-DOF serial linked arms positioned with radial symmetry about the center of each leg-base, each composed of two active and four passive joints. Walking experiments with this robot confirm that this mechanism has satisfactory performance not only as a walking robot but also as an active walking platform.

Development of walking manipulator with versatile locomotion

At present, robots are demanded not only for stationary use but also for tasks that require high mobility. The important abilities for such robots are both moving and task performing abilities. However, in order to perform tasks and move using separate mechanisms, robots are required to have many degrees of freedom (DOF). As a result, robots become heavy and lose mobility. In this paper, an effective design of robots with reduced-DOF is described. Besides, an 8-DOF bipedal configuration robot with high tasking and moving performance was developed. In this robot, the DOF have been reduced as much as possible without hampering its mobility, finding a balance between the increase in weight with additional DOF and the loss of manipulability with reduction of DOF. Moreover, applying this concept to the locomotion using the same DOF for differential purpose, it is possible to use the sane mechanism for the legged locomotion and wheeled locomotion. In this paper, this concept and maneuvers for locomotion are described. New experimental model is designed and experiment results for proposed locomotive maneuvers are expressed.

Rough terrain locomotion of a leg-wheel hybrid quadruped robot

This paper proposes a new mechanism and control method of 4-leg-wheel hybrid locomotion. Many previous hybrid vehicles execute wheel-mode and leg-mode alternatively. However, to overcome higher obstacle with sufficient velocity, a wheel locomotion should continuously be executed. In this paper, suitable load distribution control is proposed considering a contact force to the ground and step edge, a wheel driving torque, and a friction coefficient of the wheel and terrain. In a proposed new leg-wheel hybrid mechanism, load distribution control is realized by a torque of twisting joint at the center of the body, and a forward/backward shift of the body. The validity of this control and mechanism is confirmed by some experiments, where vehicle can run over a 105 mm step by 90 mm radius wheels with a good continuous movement. With an adjustment control of the approach angle, a robot can also ride over a 230 mm step