Ryder C. Winck

A novel approach to fabric control for automated sewing

This paper describes a novel fabric manipulation method for fabric control during the sewing process. It addresses issues with past attempts concerning fabric position and tension control. The method described involves replacing the current sewing feed mechanism with a servo controlled manipulator to both feed and control the fabric. The manipulator is coupled with a machine vision system that tracks the threads of the fabric to provide real-time position control that is robust with respect to fabric deformations. A prototype of the manipulator is used to demonstrate the feasibility of the concept, reaching accelerations up to 27 gs and following a closed loop trajectory with open loop control while operating in coordination with an industrial sewing machine. The system described also offers a general solution to high accuracy and high acceleration position control systems.

Time-delayed teleoperation for interaction with moving objects in space.

Telerobotics has the potential to facilitate the repair of satellites in geosynchronous orbit by allowing human operators to interact naturally with remote objects. Time delays on the order of seconds make it difficult to provide immersive feedback to the operator, motivating the use of predictive visual and haptic displays of the robot and environment. A teleoperation framework developed for this scenario invokes a two-part environment model that predicts motion of objects in the environment, both in free space and during contact with the robot. When objects in the environment are in free space, a propagated model using delayed data provides predictive feedback to the operator. However, when the robot interacts with the environment, a local environment model that does not propagate delayed data is used. This reduces computational load and ensures stability during robot-environment interactions. Two experiments were carried out to test the teleoperation system. Results demonstrate the ability of the prediction algorithm to provide reliable feedback and improve operator performance before, during, and after robot-environment interactions.

Dimension reduction in a feedback loop using the SVD: Results on controllability and stability ☆

Abstract This paper presents a method to decrease the number of inputs needed to control a system comprised of a large set of subsystems. The method couples the inputs of the subsystems using a row–column structure, thus reducing the number of inputs from m n to m + n . The resulting underactuated system is shown to maintain complete controllability if the subsystems are decoupled. Feedback for the entire system is performed by reducing the dimension of the subspace of the control inputs from a high dimension to one dimension using singular value decomposition. A stability condition for this feedback loop is presented based on the small gain theorem. In addition, the effect of the dimension reduction is explained using a simulation example.

The SVD System for First-Order Linear Systems

This brief presents theoretical guarantees for stability and performance for the singular value decomposition (SVD) system with subsystems that are linear and first order. The SVD system reduces the dimension of the control input. It is used to meet the rank-one input constraint imposed by the row-column structure. The row-column structure reduces the number of inputs required to control mn subsystems to m + n. Although the subsystems are linear and first order, they can be dynamically coupled and are coupled nonlinearly by the SVD of the control input. Thus, the entire system is of order mn and nonlinear. Lyapunov stability and performance analysis demonstrates the effect of the SVD dimension reduction through comparisons to a system with full-rank inputs. The analysis also provides convenient methods for control design. Simulation examples demonstrate the use of the SVD system, theoretical results, and the SVD systems robustness with respect to noise and nonlinearities.

A Control Loop Structure Based on Singular Value Decomposition for Input-Coupled Systems

This paper introduces a control structure based on the singular value decomposition (SVD) to control multiple subsystems with reduced inputs. The SVD System permits simultaneous, dependent control of sets of subsystems coupled by a row-column input design. The use of the SVD differs from previous applications because it is used to obtain a low-rank approximation of desired inputs. The row-column system allows many actuators to be controlled by a few inputs. Current control methods using the row-column system rely on scheduling techniques that permit independent actuator control but are too slow for many applications. The inspiration for this new control construct is a pin array human machine interface, called Digital Clay. Some useful properties of the SVD will be discussed and the SVD System will be described and demonstrated in a simulation of Digital Clay.Copyright

A control loop structure based on semi-nonnegative matrix factorization for input-coupled systems

This paper introduces a control structure based on the semi-nonnegative matrix factorization (SNMF) to simultaneously control multiple subsystems with a reduced number of inputs. The inspiration for this new control construct is a pin array human machine interface, called Digital Clay. Digital Clay uses a row-column method to control many actuators with a few inputs. The singular value decomposition (SVD) was previously studied to simultaneously control all of the actuators when using the row-column method. However, the SVD technique is not physically implantable in the row-column structure of Digital Clay due to the non-negativity constraints of the control signal. This paper proposes a system based on the SNMF, which is a low-rank approximation method with non-negativity constraints. An SNMF algorithm is presented, and its implementation in a feedback control loop, called the SNMF System, is discussed. Simulation results demonstrate the effectiveness of the SNMF System.

Command Generation Techniques for a Pin Array Using the SVD and the SNMF

Abstract This paper presents two command generation techniques for improving the surface generation time of a pin array device, specifically a prototype called Digital Clay. The procedures use singular value decomposition (SVD) and semi-nonnegative matrix factorization (SNMF) to create intermediate surfaces that sum to a desired surface. Although the focus is on pin array control, the techniques can apply to any system with a set of subsystems coupled by the row-column input method. The row-column method allows multiple actuators to be controlled by a few inputs. Current procedures for systems using the row-column method are too slow for many applications. Recent work has improved the time response of these systems using simultaneous feedback control but can potentially create unwanted oscillatory behavior. This paper describes command generation techniques using the SVD and SNMF that maintain the improvement in time without the oscillations. Simulation results compare the two procedures to the line scanning technique used in previous work on pin arrays.

Model-Mediated Teleoperation With Predictive Models and Relative Tracking

This paper presents a model-mediated approach for teleoperation with haptic feedback in the presence of time delays on the order of seconds. The target application for the control scheme is teleoperation of robotic manipulators for space systems in geosynchronous orbit. Previous work in model-mediated teleoperation allowed operators to interact with a virtual model of the remote robot and environment, where the remote robot follows the operator’s commands after a delay and the virtual model is updated when the remote data is available. Our approach adds predictive models, mediated command execution, and a dynamic slave model. A single-degree-of-freedom experiment using a simulated robot and environment demonstrate improvements in the control of remote robot position and environment contact forces, in comparison to previous approaches.© 2013 ASME

Reducing Bandwidth Usage for Controlling Systems with many Actuators

The advent of digital networks has considerably simpli ed the design and management of complex control systems, by reducing the need for dedicated communication lines between computers, actuators, and sensors. Instead, all actuators and sensors are part of the same communication line. They can be individually addressed through the assignment of unique identi ers. Such communication architectures are commonplace in modern commercial and military aviation, for which speci c communication standards, such as Mil-Std1553 or ARINC 429, have been established. They are also standard in automobiles, with the wide usage of the CAN digital communication bus. In this paper, we are interested in control systems where a large number of smart, networked actuators are present. For high-bandwidth applications, such as segmented telescopes and exible aero-elastic wings, addressing actuator individually may not be possible due to communication bandwidth limits. Previous approaches for designing computer-controlled systems with large numbers of actuators include Yook and Tilbury. Likewise, Lin and Crawley were concerned with the distributed control of an aeroelastic wing with many piezo-electric actuators. The authors proposed that actuators be grouped into a few ’superactuators’ based on openand closed-loop controllability metrics to reduce the number of communication links from the control computer to the actuators. Minor extensions of Crawley and Lin’s work have been proposed since. In a recent paper, Winck and Book consider a related problem controlling digital clay. Due to speci c mechanical constraints, collective addressing of speci c groups of clay elements are shown to be much more preferrable to individual clay element addressing, a point that motivated the present study. This note builds upon that of Lin and Crawley, by leveraging the advances in digital networking technologies that have happened since their work was published. Although very di erent from the topic addressed in this paper, the work of Winck and Book also constitutes a core inspiration for the work presented here. In our approach, the vector space of control inputs is analyzed to identify the low-dimensional, ’control subspace’ spanned by the closed-loop control activity. Next, ’virtual actuators’, are designed to approximately span the entire control subspace. Typically, the number of virtual actuators is much smaller than the original set of actuators, resulting in signi cant communication bandwidth reduction. Unlike the architecture proposed by Lin and Crawley, the same physical actuator can contribute to more than one virtual actuator. The rest of this paper is organized as follows. First, we formally introduce the linear system to be controlled, and we state the tracking problem to be solved. We then introduce full-state and output feedback controllers that solve the tracking problem. For both controllers, we describe a procedure to build virtual actuators. We then illustrate our approach by means of a numerical example, and we discuss the implementation of the virtual actuators in reduced-bandwidth communication architectures.

Tensor decomposition for control of many systems with reduced inputs

This paper proposes the use of a multi-dimensional grid to reduce the number of inputs required to control a large set of systems. This can allow for thousands of systems to be controlled by tens of inputs, saving resources and reducing complexity. Tensor decomposition, more specifically canonical decomposition and parallel factorization (CP), is used to determine the control input signals so that they are optimally close to independently controlling all the systems. The tensor decomposition is found using alternating least squares (ALS), and properties of this algorithm are utilized in a passivity proof that provides a way to verify the stability of the feedback system, which we call the CP-ALS System. The performance of the CPALS System is also examined by comparing its system response to that of the same system with independent control. This comparison reveals how the CP-ALS System works and how it is able to maintain nearly the same level of performance for many applications while reducing the number of inputs by potentially multiple orders of magnitude.