Torque control of a spherical machine with variable pole pitch

The planar motor and the spherical motor presented in this paper possess three degrees of freedom in motion. For this type of motor, special drive components and new control algorithms have to be developed because the machine operates with a variable pole pitch. The implemented control uses nonlinear force characteristics to control force and torque. It is proven that position control can be very accurate, despite the fact that the calculated and measured force characteristics contain uncertainties and errors. Simulations and experiments show that the spherical motor offers a high force and torque generation capability combined with a very precise position control. A planar motor based on the same working principle was built first to test the components and control strategies.

We synthesized two kinds of poly(9,9-diochtylfluorene) (PDOF) with different molecular weight distribution. One is PDOF with low weight molecular component (PDOF-l) and the other is PDOF with high molecular component (PDOF-h). The latter showed twice higher PL efficiency than the former. We investigated PL spectra and EL properties of the blended specimens of two PDOFs. The increase in PDOF-l content reduced PL intensity, conduction current at a constant voltage, and EL efficiency. We suggested the model due to excimer formation caused by the degree of freedom in motion of edge groups.

In this paper, Haptic End-effector for Medicine and Manufacturing (HEM2) with five degree of freedom (DoF) motion is developed for safer and more intuitive robotic surgery. In resent years, multi DoF forceps robots have been studied and developed to support surgeons. However, conventional multi DoF forceps robots cannot transmit force sensation to surgeons adequately. Force sensation is important for safe and accurate teleoperation. In this paper, a master-slave five DoF HEM2 is developed as a haptic forceps robot. Five DoF motion corresponds with the motion of human hand which can realize complex tasks. By implementing acceleration based bilateral control, force sensation can be transmitted. Spherical joint driven by parallel link mechanism realizes the bending motion of the end-effector. The coaxial driving power transmission mechanism is used to decrease the weight of movable part and improve backdrivability. Besides, the mechanism is composed of rigid parts. The performance of the five DoF HEM2 is validated by experiments.

Compared with transmission systems assembled by some single degrees-of-freedom (DOF) electrical motors, three DOF motion can be achieved in a single permanent magnet (PM) spherical motor, which is a new research direction in the field of electrical motors. The structure and operation principle of a novel PM spherical motor are introduced. An effective three dimensional (3-D) electromagnetic torque finite element model of the PM spherical motor is established, and based on the model simulation is made about the torque which can drive the motor spin. The known motor prototype is analyzed and the typical torque characteristics of the motor are derived. Through analyses of torque characteristics, a method is derived which can effectively enhance the output torque of the PM spherical motor. With the results, theoretical guide is provided for configuration optimization and torque control of the PM spherical motor.

To study the effect of food flow rheology on the human esophageal swallowing process, a biologically inspired actuator prototype has been developed. The actuator is made of silicone rubber where smooth and continuous peristaltic motion is generated by inflating air chambers distributed within its body. The soft material gives the actuator intrinsic compliance and infinite degrees of freedom in motion. Thus, it is challenging to model the behavior online by current methods. In order to investigate the large-scale deformation of the soft-bodied actuator in response to the air chamber pressures, a geometrically simplified two-dimensional (2-D) model composed of separated beam-shaped elements is proposed. It considers the mechanical properties of the material, the sophisticated geometry of the actuator as it deforms, and the distributed pressure behavior. Empirical data from the actuator prototype (captured by articulography) and the simulated results are compared to investigate the accuracy of the model. The differences of deformations between the experimental results and the theoretical model are analyzed.

In this paper the design of a 130 kW linear electric machine for use in dry gravity storage system is presented. The linear electric machine makes use of a hybrid permanent magnet vernier machine with consequent poles. The linear machine is optimally designed for a 100 m high shaft for primary response application, raising and lowering a piston of 50 tons. A speed and current control system is designed for the speed control of the piston and to determine the response time from command to full power of the piston system. The results show that the proposed hybrid permanent magnet vernier machine is well suited for primary response application. A response time of 2 seconds is found for the system, which makes it ideal for grid frequency stability.

This paper addresses determination of Degrees of Freedom (DOF) in any planar, spatial, or a combined planar-spatial mechanism. The mechanisms under study may have multiple planar and/or spatial closed loops, open chains with links in series, and/or a combination of the two. It is seen that equations available in the literature to calculate the DOF of such general mechanisms with special joint arrangements such as adjacent joints with parallel and/or intersecting axes over-predict the “true” mobility of links. To overcome this difficulty, new concepts as the Degrees of Freedom of Motion (DOFM) and Degrees of Freedom of Workspace (DOFW) have been introduced. The new definition of Degrees of Freedom of Motion yields a tight upper bound on the connectivity between any two links of a mechanism containing neighboring joints with parallel and/or intersecting joint axes.

Autonomous underwater vehicles (AUVs) are poised to become an indispensable tool for ocean exploration, underwater research and development, and military activities. One of the key elements of these vehicles is dependability; there must be some form of fault recovery/fault tolerance in the control system. In this work, we use an approach involving synthesis of motions in degrees of freedom (DOF) that are unactuated, by combining motions in DOF that are actuated. The objective is to determine the usefulness of the method for a typical streamlined vehicle which is controlled by control surfaces rather than thrusters. We find that the method has difficulties in its present form because of the righting moment designed into the vehicle, but it is functional on a modified model of the vehicle.

DragonFlex – Smart Steerable Laparoscopic Instrument

With the growing interests and high requirements in low-speed linear drives, the linear machines possessing high force density, high power density and high efficiency feature become in great demands for the linear direct-drive applications. There are many available linear machine topologies, but their performances for exhibiting the high-force density capability dissatisfy the industrial requirements. In order to solve this problem, the new machine topologies emphasizing on high force density are explored and studied. The objective of this thesis is to present the design, analysis, and application of permanent magnet (PM) linear machines which can offer a higher force density at the same magnetic loading and electric loading than the conventional machines.\n\n\n\nAlthough in recent years there are many emerging advanced PM rotational machines for direct-drive rotational drives, the development of advanced PM linear machines for direct-drive linear drives is sparse. In spite of the motion type of electric machines, the inherent operating principle is the same. By studying and borrowing concepts of the high torque density rotational electric machines, the linear machine morphologies of the promising candidates are designed and analyzed. The problems and side effects resulting from the linearization are discussed and suppressed.\n\n\n\nTwo main approaches for machine design and analysis are developed and applied, namely the analytical calculation and the finite element method (FEM). By analytically solving the magnetic field problem, the relationships between the field quantities and the machine geometry are unveiled. With the use of analytical calculation, the machine design and dimension optimization are conveniently achieved. With the use of FEM, the machine design objective and its electromagnetic performance are verified and evaluated.\n\n\n\nFinally, the proposed low-speed PM linear machine is applied for direct-drive wave power generation. By mathematically modeling the wave power, generation system and the generator, the conditions for maximum power harvesting are determined. By using the vector control, the generator output power is maximized which is verified by the simulation results.

The purpose of this research is to simulate high degree of freedom motions with low degree of freedom motions. It breaks the rule of using high degree of freedom to simulate high degree of freedom motions. Besides, except for using expensive servo slider, the study uses cables to control the simulator to reach the purpose of simulating unlimited space with limited space of the simulator and it also reach the demands of low cost. In the research, the operator’s tactile sense in body is simulated; the “visual helmet” is also added. Compared with the traditional infrared transmission, it is faster and the changes of the produced environments are more immediate. This makes the operator feels more realistic in the variation of the virtual scenes. The combination of the cable controlled simulator and the visual helmet with the software of virtual reality games makes the operator obtain more actual simulating effects in visual, audio feedback and tactile, motion feedback. It makes operator feel as if s/he is in the real world.

This paper presents the design, fabricate and evaluation of a Magnetic Resonance compatible finger rehabilitation device, which could not only be used as a finger rehabilitation training tool after stroke, but also to study the brain's recovery process during the rehabilitation therapy (ReT). The mechanics of this device are designed to be adjustable to different persons' finger phalanges, and also the gap between one finger to another can be easily changed. By using an ultrasonic motor as its actuator, the device has been designed to be portable, with a high torque output. In addition, the mechanical has been developed into two working models (passive and active) in order to overcome the intrinsic shortage of non-back drivability in ultrasonic motor. The result system enables the client to do extension and flexion rehabilitation exercises in two degrees of freedom (DOF) for each finger as well as one DOF motion on the thumb. Finally, experiment has been carried out to evaluate the performance of the device.

This paper is the first in a two-part series analyzing human arm and hand motion during a wide range of unstructured tasks. The wide variety of motions performed by the human arm during daily tasks makes it desirable to find representative subsets to reduce the dimensionality of these movements for a variety of applications, including the design and control of robotic and prosthetic devices. This paper presents a novel method and the results of an extensive human subjects study to obtain representative arm joint angle trajectories that span naturalistic motions during Activities of Daily Living (ADLs). In particular, we seek to identify sets of useful motion trajectories of the upper limb that are functions of a single variable, allowing, for instance, an entire prosthetic or robotic arm to be controlled with a single input from a user, along with a means to select between motions for different tasks. Data driven approaches are used to discover clusters and representative motion averages for the wrist 3 degree of freedom (DOF), elbow-wrist 4 DOF, and full-arm 7 DOF motions. The proposed method makes use of well-known techniques such as dynamic time warping (DTW) to obtain a divergence measure between motion segments, Ward's distance criterion to build hierarchical trees, and functional principal component analysis (fPCA) to evaluate cluster variability. The emerging clusters associate various recorded motions into primarily hand start and end location for the full-arm system, motion direction for the wrist-only system, and an intermediate between the two qualities for the elbow-wrist system.

Permanent magnet (PM) machines possess the merits of high torque density and high efficiency which is very suitable for some applications such as electric vehicles (EVs) [1]-[4]. Over the years, the surface PM and interior PM types, have been extensively studied and developed. The 2004 prius interior PM machine with the advantages of high torque density and wide speed range has been built and applied successfully in hybrid EVs. Recently, PM vernier (PMV) machines derived from magnetic gears are acknowledged that it can offer higher torque density than conventional one [4]-[6]. Unfortunately, similar to conventional PM machines, the PMV ones also suffer from relatively low flux adjusting efficiency and poor performance at high speed range due to the uncontrollable PM magnetic field. A flux controllable PMV machine has been proposed to improve these problems by the introduction of DC field excitation windings [6]. Although the flux controllable PMV machine definitely combines the merits of high torque density and wide speed range, its flux adjustment capability is still limited because the flux by the field excitation windings goes through the high magnetic reluctance of PMs. In addition, it suffers from the problems of mechanical integrity and thermal instability since the PMs are located on the rotor. To solve these problems in the existing flux controllable PMV machine, two novel hybrid excitation PMV machines with surface and V shape PMs, termed as the hybrid excitation surface PM vernier (HE-SPMV) and hybrid excitation V shape interior PM vernier (HE-VIPMV) machines, will be proposed in this paper.

Abstract. The rotor of a floating wind turbine is subject to complex aerodynamics due to changes in relative wind speeds at the blades and potential local interactions between blade sections and the rotor near wake. These complex interactions are not yet fully understood. Lab-scale experiments are highly relevant for capturing these phenomena and provide means for the validation of numerical design tools. This paper presents a new wind tunnel experimental setup able to study the aerodynamic response of a wind turbine rotor when subjected to prescribed motions. The present study uses a 1:148 scale model of the DTU 10 MW reference wind turbine mounted on top of a 6 degrees of freedom parallel kinematic robotic platform. Firstly, the thrust variation of the turbine is investigated when single degree of freedom harmonic motions are imposed by the platform, with surge, pitch and yaw being considered in this study. For reduced frequencies greater than 1.2, it is found that the thrust variation is amplified by up to 150 % compared to the quasi-steady value when the turbine is subject to pitch and surge motions, regardless of the amplitude of motion. A similar behaviour is also noticed under yaw motions. Secondly, realistic 6 degrees of freedom motions are imposed by the platform. The motions are derived from FAST simulations performed on the full-scale turbine coupled with the TripleSpar floater, and the tests aim at exploring the thrust force dynamics for different sea states and wind conditions, obtaining reasonable agreement with the simulations. Finally, the work shows the capabilities of an off-the-shelf hexapod to conduct hybrid testing of floating offshore wind turbines in wind tunnels, as well as its limitations in performing such tests.