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Kinematic design and commutation of a spherical stepper motor
 IEEE/ASME Transactions on Mechatronics
, 1999
"... Abstract—This paper addresses the design and commutation of a novel kind of spherical stepper motor in which the poles of the stator are electromagnets and the poles of the rotor (rotating ball) are permanent magnets. Due to the fact that points on a sphere can only be arranged with equal spacing in ..."
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Abstract—This paper addresses the design and commutation of a novel kind of spherical stepper motor in which the poles of the stator are electromagnets and the poles of the rotor (rotating ball) are permanent magnets. Due to the fact that points on a sphere can only be arranged with equal spacing in a limited number of cases (corresponding to the Platonic solids), design of spherical stepper motors with fine rotational increments is fundamentally geometrical in nature. We address this problem and the related problem of how rotor and stator poles should be arranged in order to interact to cause motion. The resulting design has a much wider range of unhindered motion than other spherical stepper motor designs in the literature. We also address the problem of commutation, i.e., we determine the sequence of stator polarities in time that approximate a desired spherical motion. Index Terms—Circle packing, rotation group, spherical motor. I.
Concept development and design of a spherical wheel motor (SWM
 In the IEEE International Conference on Robotics and Automation
, 2005
"... Abstract: This paper presents the design concept, models, and openloop control of a particular form of a variablereluctance spherical motor (VRSM), referred here as a spherical wheel motor (SWM). Unlike existing spherical motors where design focuses have been on controlling the three degrees of f ..."
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Cited by 7 (1 self)
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Abstract: This paper presents the design concept, models, and openloop control of a particular form of a variablereluctance spherical motor (VRSM), referred here as a spherical wheel motor (SWM). Unlike existing spherical motors where design focuses have been on controlling the three degrees of freedom (DOF) angular displacements, the SWM offers a means to control the orientation of a continuously rotating shaft in an openloop (OL) fashion. We provide a formula for deriving different switching sequences (full step and fractional step) for a specified current magnitude and pole configurations. The concept feasibility of an OL controlled SWM has been experimentally demonstrated on a prototype that has 8 rotor permanentmagnet (PM) polepairs and 10 stator electromagnet (EM) polepairs.
Miniature Direct Drive Rotary Actuators II: Eye, Finger and Leg
 Robotics and Autonomous Systems
, 1993
"... We have developed miniature direct drive DC motor actuators for robotics. These actuators have low friction, small size, high speed, low construction cost, no gear backlash, operate safely without the use of limit switches and generate moderate torque at a high torque to weight ratio. Our initial ex ..."
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Cited by 7 (1 self)
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We have developed miniature direct drive DC motor actuators for robotics. These actuators have low friction, small size, high speed, low construction cost, no gear backlash, operate safely without the use of limit switches and generate moderate torque at a high torque to weight ratio. Our initial experiments indicated the feasibility of constructing a variety of new high speed low cost actuators, for applications in camera pointing, robot hands, and robot legs. In this work we study some prototype devices in each of these categories. 1 Introduction Electromagnetic devices remain the most viable form of robot actuator, due to their relatively high strength, their well understood characteristics, the ease of interfacing them to electronic control circuits, and the nearly universal availability of electricity as a power source. Moreover, there is ongoing steady advance in electric motor component technology including permanent magnets, permeable materials, power transistors, bearings and...
NEURAL NETWORK BASED MULTISENSOR FUSION IN A NOVEL PERMANENT MAGNET MULTIDOF ACTUATOR ORIENTATION DETECTION SYSTEM
"... Abstract The methods of multiDOF actuator orientation detection based on machine vision and magnetic field sensor and neural network based multisensor fusion are presented in this paper. Special grid pattern is printed on the surface of rotor according to the pseudorandom encoder for the camera c ..."
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Abstract The methods of multiDOF actuator orientation detection based on machine vision and magnetic field sensor and neural network based multisensor fusion are presented in this paper. Special grid pattern is printed on the surface of rotor according to the pseudorandom encoder for the camera capturing the image of the rotor. The magnetic field sensors are adopted and properly placed circling the shaft of rotor for detection the orientation information. By analyzing the image of the rotor, the coordinates of characteristic points in the coordinate system fixed on the rotor are derived. Combined with the magnetic sensor scheme to reduce the measurement error and enhance the fault tolerant ability, a multisensor data fusion scheme using BP neural network is developed and validated by experiment. The results show that multisensor data fusion based on NN is superior to single
Mathematical models of binary sphericalmotion encoders
 IEEE/ASME Transactions on Mechatronics
"... Abstract—This paper presents several algorithms that solve the problem of determining the orientation of a freely rotating ball that is partially enclosed in a housing. The ball is painted in two colors (black and white) and the housing has a number of sensors that detect these colors. The question ..."
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Cited by 3 (1 self)
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Abstract—This paper presents several algorithms that solve the problem of determining the orientation of a freely rotating ball that is partially enclosed in a housing. The ball is painted in two colors (black and white) and the housing has a number of sensors that detect these colors. The question we answer is: Knowing how the ball is painted, knowing the location of the sensors, and given a complete set of sensor measurements, how does one determine the orientation of the ball to within an acceptable error threshold? The algorithms we present to solve this problem are based on methods and terminology from geometric control theory. Essentially, we generate dynamical systems that evolve on the group (3). These dynamical systems are constructed so as to attract the computed orientation of the ball to the actual one being detected by the sensors. Solving this spherical decoding problem is important in applications where spherical motion must be detected. One such application is the feedback control of spherical motors. Index Terms—Gradient descent, nonsmooth optimization, optical encoder, rotation group, spherical motion. I.
Determining the Orientation of a Painted Sphere from a Single Image: A Graph Coloring Problem
, 2001
"... In our work on robotic manipulation, we required a method for determining the orientation of a marked sphere from a single visual image. Our solution utilizes features of different colors painted on the sphere at the vertices of the Platonic solids. The main result of this paper is the minimization ..."
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In our work on robotic manipulation, we required a method for determining the orientation of a marked sphere from a single visual image. Our solution utilizes features of different colors painted on the sphere at the vertices of the Platonic solids. The main result of this paper is the minimization of the number of feature colors needed to solve the correspondence problem. The minimization of colors is a graph coloring problem. Index Terms  Graph coloring, feature correspondence, Platonic solids, surface markings, sphere orientation. 1
Design optimization of a three degreesoffreedom variablereluctance spherical wrist motor
 ASME J. Eng. Ind
, 1995
"... This paper presents the basis for optimizing the design of a three degreesoffreedom (DOF) variable reluctance (VR) spherical motor which offers some attractive features by combining pitch, roll, and yaw motion in a single joint. The spherical wrist motor offers a major performance advantage in tr ..."
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Cited by 2 (0 self)
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This paper presents the basis for optimizing the design of a three degreesoffreedom (DOF) variable reluctance (VR) spherical motor which offers some attractive features by combining pitch, roll, and yaw motion in a single joint. The spherical wrist motor offers a major performance advantage in trajectory planning and control as compared to the popular threeconsecutiverotational joint wrist. Since an improved performance estimate is required, a method for optimizing the VR spherical motor's magnetics was developed. This paper begins with a presentation of the geometrical independent and dependent variables which fully described the design of a VR spherical motor. These variables are derived from examination of the torque prediction model. Next, a complete set of constraint equations governing geometry, thermal limitations, amplifier specifications, iron saturation, and leakage flux are derived. Finally, an example problem is presented where the motor's geometry is determined by maximizing the output torque at one rotor position. The concept of developing a spherical motor with uniform torque characteristics is discussed with respect to the optimization methodology. It is expected that the resulting analysis will improve the analytical torque prediction model by the inclusion of constraint equations, aid in developing future VR spherical motor designs, improve estimates of performance, and therefore will offer better insight into potential applications. 1
Effects of Adaptive Discretization on Numerical Computation using Meshless Method with Liveobject Handling Applications
, 2007
"... ..."
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"... Abstract — This paper presents a method of deriving the torque model for a three degrees of freedom (3DOF) spherical motor such as a variablereluctance spherical motor (VRSM) or a spherical wheel motor (SWM). The SWM (much like the VRSM capable of offering threeDOF in a single joint) offers the a ..."
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Abstract — This paper presents a method of deriving the torque model for a three degrees of freedom (3DOF) spherical motor such as a variablereluctance spherical motor (VRSM) or a spherical wheel motor (SWM). The SWM (much like the VRSM capable of offering threeDOF in a single joint) offers the ability to spin continuously while the rotor shaft can be tilted arbitrarily. We derive a closedform torque model and demonstrate its use for designing the switching controller based the principle of pushpull operation for the SWM. The closedform torque model given here greatly reduces the torque computation, and simplifies the design of the switching controller. Keywords actuators, torque model, stepper control I.
Novel 3DOF Reconfigurable Spherical Motion Generator with Unlimited Workspace
"... In this paper, an innovative Reconfigurable Spherical Motion Generator (RSMG) is introduced to provide continuous spherical motion and force transmission. The mechanism enables unlimited workspace in 3DOF spherical motion with rapid, continuous and precise motion capability. The conceptual design, ..."
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In this paper, an innovative Reconfigurable Spherical Motion Generator (RSMG) is introduced to provide continuous spherical motion and force transmission. The mechanism enables unlimited workspace in 3DOF spherical motion with rapid, continuous and precise motion capability. The conceptual design, as well as direct and inverse kinematics, are presented here. Singularities of the mechanism are analyzed. An actuation strategy is proposed such that the RSMG is capable of avoiding any types of singularities in order to produce unlimited spherical motion. 1