Flight Evaluation of an Adaptive Velocity Command System for Unmanned Helicopters

Limited by supply voltage on board, control accuracy of low velocity and available torque of Control Moment Gyros (CMGs) gimbal driving motor are limited. Adding Harmonic Drive (HD) between driving motor and CMGs gimbal can improve CMGs control system performance. The paper establishes a practical HD model considering transmission, bearing friction, tooth meshing friction and compliance of flexspline. The model is properly simplified for analysing the control performance of whole closed loop system. Transfer functions are analysed and the flexspline output velocity is chosen to be the velocity feedback for controller according to the characteristics of CMGs gimbal velocity command. All of the numerical simulation results validate the theory analysis.

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Handheld Robot for Bone Drilling Assistance

10.29007/pzrj ◽

2018 ◽

Author(s):

Ping-Lang Yen ◽

Shuo-Suei Hung

Keyword(s):

Computer Navigation ◽

Human Operator ◽

Navigation Systems ◽

Bone Drilling ◽

Drilling Force ◽

Robot Controller ◽

Tool Positioning ◽

Surgical Tool ◽

Compensation Function ◽

Velocity Command

Computer navigation systems has provided useful visual guidance for the surgeon to deliberately locate the tools to the anatomy. However, the tool positioning process is still manually performed. Sometimes the tool positioning may cause fatigue, stress and might be of risk to patient too. In this paper we designed a special purpose handheld robot for bone drilling. Meanwhile the coordinated controller assists the surgeon to precisely and safely drill the bone safely. Two force sensors are embedded at the handle and the cutter to measure the human exerted force and bone drilling force, respectively. The velocity command was then computed by the admittance controller for the robot controller. The motion of the control handle is positioned by the surgeon, while the surgical tool driven by the robot end-effector. The coordination between the human operator and the robot was designed so that the bone drilling can be performed more effectively than only imagenavigation scenario. The drill was able to be maintained on the target trajectory with reasonable accuracy within 2 mm although the human operator has deviated the surgical tool up to 5 cm. The compensation function to guide the drill back to the planned path was very useful to prevent the drill’s breakage when penetrating through the holes on the bone plate in bone drilling procedure.

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Saccade–Vergence Interactions in Macaques. II. Vergence Enhancement as the Product of a Local Feedback Vergence Motor Error and a Weighted Saccadic Burst

Journal of Neurophysiology ◽

10.1152/jn.01337.2004 ◽

2005 ◽

Vol 94 (4) ◽

pp. 2312-2330 ◽

Cited By ~ 29

Author(s):

C. Busettini ◽

L. E. Mays

Keyword(s):

Feedback Loop ◽

Time Course ◽

Peak Velocity ◽

Additive Model ◽

Feedback Mechanism ◽

Common Mechanism ◽

Vertical Saccades ◽

Motor Error ◽

Local Feedback ◽

Velocity Command

In the accompanying paper we reported that intrasaccadic vergence enhancement during combined saccade–vergence eye movements reflects saccadic dynamics, which implies the involvement of saccadic burst signals. This involvement was not predicted by the Multiply Model of Zee et al. We propose a model wherein vergence enhancement is the result of a multiplicative interaction between a weighted saccadic burst signal and a nonvisual short-latency estimate of the vergence motor error at the time of the saccade. The enhancement of vergence velocity by saccades causes the vergence goal to be approached more rapidly than if no saccade had occurred. The adjustment of the postsaccadic vergence velocity to this faster reduction in vergence motor error occurred with a time course too fast for visual feedback. This implies the presence of an internal estimate of the progress of the movement and indicates that vergence responses are under the control of a local feedback mechanism. It also implies that the vergence enhancement signal is included in the vergence feedback loop and is an integral part of the vergence velocity command. Our multiplicative model is able to predict the peak velocity of the vergence enhancement as a function of cyclopean saccadic dynamics, smooth vergence dynamics, and saccade–vergence timing with remarkable precision. It performed equally well for both horizontal and vertical saccades with very similar parameters, suggesting a common mechanism for all saccadic directions. A saccade–vergence additive model is also presented, although it would require external switching elements. Possible neural implementations are discussed.

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Slow–fast control of eye movements: an instance of Zeeman’s model for an action

Biological Cybernetics ◽

10.1007/s00422-020-00845-7 ◽

2020 ◽

Vol 114 (4-5) ◽

pp. 519-532

Author(s):

Richard A. Clement ◽

Ozgur E. Akman

Keyword(s):

Eye Movements ◽

Rhesus Monkey ◽

Model Equation ◽

Oculomotor System ◽

State Space Reconstruction ◽

Model Predictions ◽

Motor Actions ◽

Fast Control ◽

Omnipause Neurons ◽

Velocity Command

Abstract The rapid eye movements (saccades) used to transfer gaze between targets are examples of an action. The behaviour of saccades matches that of the slow–fast model of actions originally proposed by Zeeman. Here, we extend Zeeman’s model by incorporating an accumulator that represents the increase in certainty of the presence of a target, together with an integrator that converts a velocity command to a position command. The saccadic behaviour of several foveate species, including human, rhesus monkey and mouse, is replicated by the augmented model. Predictions of the linear stability of the saccadic system close to equilibrium are made, and it is shown that these could be tested by applying state-space reconstruction techniques to neurophysiological recordings. Moreover, each model equation describes behaviour that can be matched to specific classes of neurons found throughout the oculomotor system, and the implication of the model is that build-up, burst and omnipause neurons are found throughout the oculomotor pathway because they constitute the simplest circuit that can produce the motor commands required to specify the trajectories of motor actions.

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Stable contour-following control of wheeled mobile robots

Robotica ◽

10.1017/s026357470800444x ◽

2009 ◽

Vol 27 (1) ◽

pp. 1-12 ◽

Cited By ~ 32

Author(s):

Juan Marcos Toibero ◽

Flavio Roberti ◽

Ricardo Carelli

Keyword(s):

Control System ◽

Mobile Robots ◽

Control Algorithms ◽

Wheeled Mobile Robots ◽

Distance Information ◽

Straight Wall ◽

The Stability ◽

Office Environments ◽

Wall Following ◽

Velocity Command

SUMMARYThis paper presents a continuous wall-following controller for wheeled mobile robots based on odometry and distance information. The reference for this controller is the desired distance from the robot to the wall and allows the robot to follow straight wall contour as well as smoothly varying wall contours by including the curvature of the wall into the controller. The asymptotic stability of the control system is proved using a Lyapunov analysis. The controller is designed so as to avoid saturation of the angular velocity command to the robot. A novel switching scheme is also proposed that allows the robot to follow discontinuous contours allowing the robotic system to deal with typical problems of continuous wall-following controllers such as open corners and possible collisions. This strategy overcomes these instances by switching between dedicated behavior-based controllers. The stability of the switching control system is discussed by considering Lyapunov concepts. The proposed control systems are verified experimentally in laboratory and office environments to show the feasibility and good performance of the control algorithms.

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