The Mathematics of Coordinated Control of Prosthetic Arms and Manipulators

1972 ◽  
Vol 94 (4) ◽  
pp. 303-309 ◽  
Author(s):  
D. E. Whitney
Keyword(s):  
Control Problem ◽  
Rate Control ◽  
Position Control ◽  
Dynamic Control ◽  
Mathematical Formulation ◽  
Coordinated Control ◽  
Computer Assisted ◽  
Final Position ◽  
Coordinate Systems ◽  
Joint Angles

The problems of coordinated rate control and position control of multidegree-of-freedom arms are treated together in this paper. A mathematical formulation is presented which allows real time computer-assisted rate control under a variety of external coordinate systems. A new solution to the endpoint position control problem is given, allowing the arm to be driven to a final position specified in meaningful external coordinates without the corresponding final joint angles being known. Attention is given to redundant arms, to the possibility of singularities, and to the relation between this work and dynamic control of arms.

Actuation Control for Nanostructured Origami™

2006 ◽  
Author(s):  
Paul Stellman ◽  
George Barbastathis
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Position Control ◽  
Control Law ◽  
Pd Controller ◽  
Joint Angles ◽  
Pd Control ◽  
Joint Torques ◽  
Corner Cube ◽  
Control Constant

The fabrication of arbitrary nanostructured devices in 3D space is relevant to many areas of academic and industrial research. From hybrid systems with various physical features to complex 3D optical interconnects, the added functionality gained by 3D nanomanufacturing is promising for the development of novel applications. Nevertheless, the 2D nature of conventional nanomanufacturing processes (i.e. lithography) underutilizes the 3rd dimension since there is currently no infrastructure for 3D. Nanostructured Origami has been proposed [1-3] as one solution to the 3D nanomanufacturing problem. The two-step process consists of first patterning devices and creases (axes of rotation) in 2D followed by a subsequent folding step which actuates the origamis to its final 3D shape. Several actuation mechanisms have been investigated for the folding step, and the folding of simple origamis with an open kinematic chain has been successfully demonstrated experimentally [1-3]. Since the origami segments must be accurately aligned in the 3D folded state, the actuation mechanisms for Nanostructured Origami must be both controllable and repeatable. By developing analytical models of the origamis, control schemes can be simulated to aid in the manufacturing of devices in the laboratory. As an example, a PD control scheme is introduced to achieve set-point position control of an example origami, the corner cube. In the laboratory, a PD control system would be built using a magnetic feedback mechanism. A strip of gold is patterned as a hinge material, and electrical current passes through the wire. In the presence of a magnetic field, the Lorentz force acts upon the origami segments and the resulting torque is given by τ = Cicos α,[Equation] where C is a positive constant, i is the current, and α is the angle between the magnetic field and the current. The PD control law for Nanostructured Origami is equivalent to PD control of an articulated robotic manipulator, with the exception that gravity can be ignored due to the low masses of the membranes. Instead, the stiffnesses of the hinges must be balanced, resulting in a control torque of [Equation] where τ is the vector of joint torques, G is the constraint Jacobian, Kp is the proportional control constant, Kd is the derivative control constant, K is the hinge stiffness matrix, q is the vector of joint angles, and qd is the desired steady-state values of the joint angles. This input torque is applied to the origami device, and the response is calculated by integrating the system's equations of motion [3]. The angular response of the PD controller for the corner cube origami is plotted in Fig. 1, and Fig. 2 shows a schematic of the folding of the corner cube from flat to folded state. Note the well-behaved response for a Kp value of 1500, which demonstrates zero overshoot and a rise time of approximately 15 milliseconds. A plot of the joint torques as a function of time is shown in Fig. 3. This abstract has briefly introduced the use of a PD controller for the actuation of origami devices. For a Lorentz force actuation scheme, we have demonstrated through simulations that the PD control law is stable and robust. If complicated 3D origamis with multiple closed kinematic chains are to be built, detailed control laws must be implemented. Advanced control techniques, such as optimal control, will be investigated to explore improved actuation strategies.

Dynamic Scheduling of a Four-Station Queueing Network

1990 ◽  
Vol 4 (1) ◽  
pp. 131-156 ◽  
Author(s):  
C. N. Laws ◽  
G. M. Louth
Keyword(s):  
Control Problem ◽  
Dynamic Scheduling ◽  
Dynamic Control ◽  
Queueing Network ◽  
Single Server ◽  
Scheduling Policies ◽  
Resource Pooling ◽  
Static Scheduling ◽  
Open Queueing Network ◽  
Dynamic Policy

This paper is concerned with the problem of optimally scheduling a multiclass open queueing network with four single-server stations in which dynamic control policies are permitted. Under the assumption that the system is heavily loaded, the original scheduling problem can be approximated by a dynamic control problem involving Brownian motion. We reformulate and solve this problem and, from the interpretation of the solution, we obtain two dynamic scheduling policies for our queueing network. We compare the performance of these policies with two static scheduling policies and a lower bound via simulation. Our results suggest that under either dynamic policy the system, at least when heavily loaded, exhibits the form of resource pooling given by the solution to the approximating control problem. Furthermore, even when lightly loaded the system performs better under the dynamic policies than under either static policy.

scholarly journals Motor learning reveals the existence of multiple codes for movement planning

2012 ◽  
Vol 108 (10) ◽  
pp. 2708-2716 ◽  
Author(s):  
Todd E. Hudson ◽  
Michael S. Landy
Keyword(s):  
Target Location ◽  
Movement Planning ◽  
Movement Direction ◽  
Final Position ◽  
Coordinate Systems ◽  
Circular Distribution ◽  
Movement Vector ◽  
Definitive Evidence ◽  
Position Code ◽  
Identical Task

Coordinate systems for movement planning are comprised of an anchor point (e.g., retinocentric coordinates) and a representation (encoding) of the desired movement. One of two representations is often assumed: a final-position code describing desired limb endpoint position and a vector code describing movement direction and extent. The existence of movement-planning systems using both representations is controversial. In our experiments, participants completed reaches grouped by target location (providing practice for a final-position code) and the same reaches grouped by movement vector (providing vector-code practice). Target-grouped reaches resulted in the isotropic (circular) distribution of errors predicted for position-coded reaches. The identical reaches grouped by vector resulted in error ellipses aligned with the reach direction, as predicted for vector-coded reaches. Manipulating only recent movement history to provide better learning for one or the other movement code, we provide definitive evidence that both movement representations are used in the identical task.

Dynamic Force-Position Control of the Walking Robots Motion on Slope

2012 ◽  
Vol 186 ◽  
pp. 98-104 ◽  
Author(s):  
Luige Vladareanu ◽  
Daniel Octavian Melinte
Keyword(s):  
Position Control ◽  
Dynamic Control ◽  
Open Architecture ◽  
Walking Robots ◽  
Robot Motion ◽  
Dynamic Force ◽  
Walking Robot ◽  
Kinematic Modeling ◽  
Dynamic Hybrid ◽  
The Stability

Abstract. The paper presents a strategy for the dynamic hybrid force-position control of the walking robot motion on slope using the ZMP method for dynamic control and a stable and robust method. Through dynamic and kinematic modeling of the walking robots motion an open architecture system was developed which contains five control interfaces. The stability problem of quadruped walking robots, through extendible segments which are designed to reduce the difficulty of walking on slope, and also by using them to avoid obstacles that may occur during a stepping cycle are presented. The results obtained have led to an improvement in the response time to disturbances, to tracking the motion trajectory with higher precision in conditions of high stability and to development of new technological capabilities, adapting the robot walking to movement over sloped terrain, with obstacles and bumps.

scholarly journals Điều khiển thích nghi vị trí trên cơ sở kỹ thuật vi xử lý Phần I: Hệ thống điều chỉnh vị trí nhờ quan sát và phản hồi trạng thái

2018 ◽  
Vol 5 (4) ◽  
pp. 10-16
Author(s):  
Pham Huy Thoa
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Control Problem ◽  
Control Algorithm ◽  
Position Control ◽  
The State ◽  
Control Algorithms ◽  
State Variable ◽  
Load Characteristics ◽  
Positional Control

  In order to investigate different position control algorithms for numerical controlled machines and robots, a positional control system was built on the base of  a microcomputer. In part I, the paper presents the  observer algorithm for  state variable estimation and the state variable feedback control algorithm applied to the position control of a  particular machine-table. With the hardware and software structure of the microcomputer based digital system described in this paper different control algorithms can be  realized flexibly. The position control problem for the plant with variations or  uncertainties of  parameters and load characteristics will be reported in part II.

Joint-angle-based yoga posture recognition for prevention of falls among older people

2019 ◽  
Vol 53 (4) ◽  
pp. 528-545
Author(s):  
Ponmozhi Chezhiyan ◽  
Deepalakshmi P.
Keyword(s):  
Older People ◽  
Joint Angle ◽  
The Elderly ◽  
Learning System ◽  
Computer Assisted ◽  
World Population ◽  
Joint Angles ◽  
Content Type ◽  
Posture Recognition ◽  
Do So

Purpose United Nations’ World Population Ageing Report states that falls are one of the most common problems in the elderly around the world. Falls are a leading cause of morbidity and mortality among mature adults, and the second leading cause of accidental or unintentional injury/death after road traffic injuries. The rates are higher in hospitalized patients and nursing home residents. Major contributing reasons for falling are loss of footing or traction, balance problem in carpets and rugs, reduced muscle strength, poor vision, mobility/gait, cognitive impairment: in other words lack of balance. Balance can be improved by the practice of yoga which helps to balance both body and mind through a series of physical postures called asanas, breathing control and meditation. Elders, especially women, are often unable to practice yoga regularly, largely brought on by a feeling of discomfort at having to do so in full public view, preferring instead to have private sessions at home, and at leisure. A computer-assisted self-learning system can be developed to help such elders, though improper training and the postures associated with it may harm the body’s muscles and ligaments. To have a flawless system it is essential to classify asanas, and identify the one the practitioner is currently practicing, following which the system can offer the guidance necessary. The purpose of this paper is to propose a posture recognition system, especially of sitting and standing postures. Asanas are chiefly classified into two: sitting and standing postures. This study helps to decide the values of the parameters for classification, which involve the hip and joint angles. Design/methodology/approach To model human bodies, skeleton parts such as head, neck (which are responsible for head movements), arms, hands (to decide on hand postures), and legs and feet (for standing posture identification) have been modeled and stored as a vector. Each feature is defined as a set of movable joints. Every interaction among the skeleton joints defines an action. Human skeletal information may be represented as a hierarchy of joints, in a parent–child relationship. So that whenever there is a change in joint its corresponding parent joint may also be altered. Findings The findings have to do with analyzing the reasons for falls in the elderly and their need for yoga as a precautionary measure. As yoga is ideally suited to self-assisted learning, it is feasible to design a system that assists people who do not wish to practice yoga in public. However, asanas are to be classified prior to doing so. In this paper, the authors have designed a posture identification framework comprising the sitting and standing postures that are fundamental to all yoga asanas, using joint angle measurements. Having fixed joint angle values is not possible, given the variations in angle values among the participants. Consequently, such parameters as the hip joint and knee angles are to be specified in range for a classification of asanas. Research limitations/implications This work identifies the angle limits of standing and sitting postures so as to design a self-assisting system for yoga. Yoga asanas are classified and tested to enable their accurate identification. Extensive testing with older people is needed to assess the system. Practical implications The increase in the population of the elderly, coupled with their need for medical care, is a major concern worldwide. As older people are reluctant to practice yoga in public, it is anticipated that the proposed system will motivate them to do so at their convenience, and in the seclusion of their homes. Social implications As older people are reluctant to adapt as well as practice yoga in public view, the proposal motivates and helps them to carry out yoga practices at their convenience. Originality/value This paper fulfills the initial study on the need and feasibility of creating a self-assisted yoga learning system. To identify postures and classify them joint angles are used; their range of motion has been calculated in order to set them as parameters of classification.

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