Spherical motors are classified as multi-degrees-of-freedom actuators. Several types of spherical motors are under investigation in the world because they will be useful for robots that currently use combination of 2 or 3 one-degree-of-freedom motors. However, most of the previous works mainly demonstrated how the motors rotate or how they output torque without giving enough specifications. Torque, velocity, efficiency, controllability, and response are important issues to determine how they can be used for robots or practical mechatronic systems. The objective of this paper is to propose a method to measure three-degrees-of-freedom torque of spherical motors while they rotate with arbitrary angular velocity, which can evaluate torque in practical situations and can be used to derive efficiency of the motor. These measurements are important for comparison among the implementations and improvement of the systems. The idea consists of two parts. One is torque measurement using a 6-axis force/torque sensor. It enables off-axis simultaneous measurement of torque. The other is an external 3-degrees-of-freedom rotor driver using wheels for omnidirectional mobile robots, which is installed between the rotor and the sensor. Detailed principles and a set of experimental measurements of our spherical induction motor demonstrating usefulness of the proposed method are described in this paper.

We give a system overview and initial experimental results for SIMbot (spherical induction motor based ballbot), a human-sized dynamically stable mobile robot with only two active moving parts. SIMbot is a qualitatively new kind of robot with the potential to drastically reduce mechanical complexity in human-sized mobile robots. SIMbot uses a novel spherical induction motor as its drive mechanism, which is mechanically simpler than other ballbot drive mechanisms. We demonstrate the feasibility of this innovation with experimental results for balancing, stationkeeping, short point-to-point motions, and recovery from initial lean angles.

This paper describes the design, construction, and operation of a closed-loop spherical induction motor (SIM) ball wheel for a balancing mobile robot (ballbot). Following earlier work, this new design has a smaller rotor and higher torques due to the use of six stators in a skewed layout. Actuation and sensing kinematics as well as control methods are presented. In its current implementation, torques of up to 8 Nm are produced by the motor with rise and decay times of 100 ms. Results are presented supporting its potential as a prime mover for mobile robots.

This paper reports, to our knowledge, the first spherical induction motor (SIM) operating with closed loop control. The motor can produce up to 4 Nm of torque along arbitrary axes with continuous speeds up to 300 rpm. The motor's rotor is a two-layer copper-over-iron spherical shell. The stator has four independent inductors that generate thrust forces on the rotor surface. The motor is also equipped with four optical mouse sensors that measure surface velocity to estimate the rotor's angular velocity, which is used for vector control of the inductors and control of angular velocity and orientation. Design considerations including torque distribution for the inductors, angular velocity sensing, angular velocity control, and orientation control are presented. Experimental results show accurate tracking of velocity and orientation commands.

This paper reports a planar induction motor that can output 70 N translational thrust and 9 Nm torque with a response time of 10 ms. The motor consists of three linear induction armatures with vector control drivers and three optical mouse sensors. First, an idea to combine multiple linear induction elements is proposed. The power distribution to each element is derived from the position and orientation of that element. A discussion of the developed system and its measured characteristics follow. The experimental results highlight the potential of its direct drive features.

Robots using ball(s) as spherical wheels have the advantage of omnidirectional motion. Some of these robots use only a single ball as their wheel and dynamically balance on it. However, driving a ball wheel is not straightforward. These robots usually use one or more motor-driven rollers or wheels in frictional contact with the ball wheel. Some slippage can occur with these schemes, so it is important to measure the actual rotation of the ball wheel for good control. This paper proposes one method for measuring the three dimensional rotation of a sphere, which is applicable to the case of a ball wheel. The system measures surface speed by using two or more optical mouse sensors and transforms them into the angular velocity vector of the ball, followed by integration to give the rotational angle. Experiments showed the correctness of this method, yielding an error of approximately 1%, with a 10 ms response.

There are several works on mobile robots that employed a single ball as their wheel. Each of them used a kind of inverted pendulum control and a specific ball drive mechanism. The requirement for the mechanism is to roll the ball in two orthogonal directions for maintaining robot attitude and traveling on a two dimensional surface. In addition to these rolling motions, rotation around a vertical axis is useful for turning the robot body. The author developed robots that used wheels for omnidirectional motion of the ball in previous works. However, the wheel was complex to produce in large quantities and expensive. The purpose of the work described in this paper is to develop a new simpler mechanism with drivability almost comparable to previous driving mechanism but lower in cost. The idea of a roller with semi-passive features and a ball drive mechanism are described as well as experimental results using a robot with the proposed mechanism.

This paper proposes a robot balanced on a ball. In contrast to an inverted pendulum with two wheels, such as the Segway Human Transporter, an inverted pendulum using a ball can traverse in any direction without changing its orientation, thereby enabling stable motion. Such robots can be used in place of the two-wheeled robots. The robot proposed in this paper is equipped with three omnidirectional wheels with stepping motors that drive the ball and two sets of rate gyroscopes and accelerometers as attitude sensors. The robot has a simple design; it is controlled with a 16-bit microcontroller and runs on Ni-MH batteries. It can not only stand still but also traverse on floor and pivot around its vertical axis. Inverted pendulum control is applied in two axes for attitude control, and commanded motions are converted into velocity commands for the three wheels. The mechanism, control method, and experimental results including application to transport are described in this paper.

Many of autonomous robots or industrial robots require three-dimensional environmental sensors. Stereo visions or laser range finders are often used to detect distance to obstacles or targets. A new type of three-dimensional measurement system is proposed in this paper. This method is a kind of active stereo vision based on light-section method and phase-shift method. A special light source that consists of a rotating cylinder and a lamp is used. It projects planes of lights whose intensities vary in a sinusoidal function of time. Phase of each plane is different from those of other plane, and we can distinguish which plane sectioned the target from the phase. The images obtained from video camera are processed into phase of each pixel that indicates distance to measuring targets. The method needs only simple calculation for the detection of phase. The basic principle and expanded methods for practical use are proposed in this paper. The experimental results using trial system are also given, which show effectiveness of the method.

Walking robots are useful for uneven terrain where wheels or crawlers are unsuitable. The biped robot is a kind of walking robot that we can use under human-live environments. There are many research works on biped robots. The biped robots need ability to adapt itself to uneven or non-horizontal plane if we want to use them in our environment although the robots walked on flat horizontal plane or fixed inclined plane in most of these works. In this paper, we propose a control method for walking of biped robots on undulating ground. This method contains grade estimation of ground using stereo vision and walk of robot on slope. Experimental results that indicate ability of this method are also shown.