Gary McMurray

Uncalibrated dynamic visual servoing

A dynamic quasi-Newton method for uncalibrated, vision-guided robotic tracking control with fixed imaging is developed and demonstrated. This method does not require calibrated kinematic and camera models. Robotic control is achieved at each step through minimizing a nonlinear objective function, by taking quasi-Newton steps and estimating the composite Jacobian at each step. The Jacobian is estimated using a dynamic recursive least-squares algorithm. Experimental results demonstrate the validity of this approach.

A dynamic Jacobian estimation method for uncalibrated visual servoing

A dynamic Broydens method is presented for use in a quasi-Newton control scheme for model-independent vision guided robotic control. Model independent visual servo control is defined as using visual feedback to control a robot without precisely calibrated kinematic and camera models. The control problem is formulated as a nonlinear least squares optimization. For the moving target case, this results in a time-varying objective function which is minimized using a dynamic Newtons method. The dynamic Jacobian estimation scheme is used to estimate the combined robot and image Jacobians. Experimental results for a two-degree-of-freedom system demonstrates the success of the algorithm.

Tracking a moving target with model independent visual servoing: a predictive estimation approach

Target tracking by model independent visual servo control is achieved by augmenting quasi-Newton trust region control with target prediction. Model independent visual servo control is defined using visual feedback to control the robot without precise kinematic and camera models. While a majority of the research assumes a known robot and camera model, there is a paucity of literature addressing model independent control. In addition, most researches have focused primarily on static targets. The work presented here demonstrates the use of predictive filters to improve the performance of the control algorithm for linear and circular target motions. The results show a performance of the same order of magnitude as compared to some model based visual servo control research. Certain limitations to the algorithm are also discussed.

Cutting, 'by pressing and slicing', applied to the robotic cut of bio-materials. II. Force during slicing and pressing cuts

The applications of robotics are becoming more and more common in non-traditional industries such as the medical industry including robotic surgery and sample microtoming as well as food industry that include the processing of meats, fruits and vegetables. In this paper, the influence of the blade edge-shape and its slicing angle on the cutting of biomaterials are formulated and discussed based on the stress analysis that has been presented in part I. Through modeling the cutting force, an optimal slicing angle can be formulated to maximize the feed rate while minimizing the cutting forces. Moreover, the method offers a means to predict cutting forces between the blade and the biomaterials, and a basis for design of robust force control algorithms for automating the cutting of biomaterials

All Silicon Micro-GC Column Temperature Programming Using Axial Heating

In this work we present a high performance micro gas chromatograph column with a novel two dimensional axial heating technique for faster and more precise temperature programming, resulting in an improved separation performance. Three different axial resistive heater designs were simulated theoretically on a 3.0 m × 300 μm × 50 μm column for the highest temperature gradient on a 22 by 22 μm column. The best design was then micro-fabricated and evaluated experimentally. The simulation results showed that simultaneous temperature gradients in time and distance along the column are possible by geometric optimization of the heater when using forced convection. The gradients along the column continuously refocused eluting bands, offsetting part of the chromatographic band spreading. The utility of this method was further investigated for a test mixture of three hydrocarbons (hexane, octane, and decane).

Uncalibrated target tracking with obstacle avoidance

Target tracking and obstacle avoidance are demonstrated for uncalibrated visual servoing. An objective function is designed that encourages target following by a robotic end-effector while discouraging movements near an obstacle. The objective function incorporates the error between the target and the end-effector and a potential function related to the obstacle. This objective function is minimized using a dynamic nonlinear least squares optimization method in conjunction with a recursive least squares Jacobian estimation algorithm. The approach is generic and can be applied to a variety of systems. Calibration is unnecessary after a reconfiguration or disturbance to the robotic workcell. This type of control has the potential to provide a low-cost, low-maintenance automation solution for unstructured industries and environments. Experimental results demonstrate both target tracking and obstacle avoidance for an uncalibrated robotic system.

Uncalibrated visual servoing for intuitive human guidance of robots

We propose a novel implementation of visual servoing whereby a human operator can guide a robot relative to the coordinate frame of an eye-in-hand camera. Among other applications, this can allow the operator to work in the image space of the eye-in-hand camera. This is achieved using a gamepad, a time-of-flight camera (an active sensor that creates depth data), and recursive least-squares update with Gauss-Newton control. Contributions of this paper include the use of a person to cause the control action in a visual-servoing system, and the introduction of uncalibrated position-based visual servoing. The systems efficacy is evaluated via trials involving human operators in different scenarios.

Modeling of blade sharpness and compression cut of biomaterials

To realize the automation of biomaterial cutting, the interaction between the blade and biomaterial deserves insight understanding. In this paper, a blade-compression cutting model is developed. The influences from the material properties, deformation, and blade properties on the cutting force are thoroughly explained. An approach to describe the sharpness of a blade is provided and its applicability is experimentally demonstrated. Based on the material property and knife sharpness property, the required force to realize compression cut can be predicted. This provides the reference force trajectory for the automation of biomaterial compression cutting.

Experimental results using vision-based control for uncalibrated robotic systems

This work demonstrates a vision-based control technique that does not require robot or vision system calibration. There are two distinct advantages: first, the approach is generic and can be applied to a variety of systems; second, calibration is unnecessary after a reconfiguration or disturbance to the robotic workcell. It has the potential to provide a low-cost, low-maintenance automation solution for unstructured industries and environments. The robot end- effector tracks a moving target using a novel dynamic quasi- Newton control was formulated in the image plane and on-line Jacobian estimation using either a dynamic Broydens method or a dynamic recursive least squares algorithm. Experimental results demonstrate convergent and stable control of an uncalibrated manipulator tracking a moving target. The method is shown to be robust to system reconfiguration such as modifications to the position and orientation of the camera.

Intelligent automation of bird deboning

Second and further processing operations constitute the largest use of on-the-line labor in todays poultry processing plants. Deboning is a significant part of these operations. This paper describes continuing work in the intelligent automation of bird deboning, a task that is conceptualized into three parts: characterizing the non-uniform bird product (using statistical studies and image processing), obtaining a nominal cutting path (using image features correlated to internal bird structures and robot kinematics), and correcting for deviations from the nominal cutting path (using force control). Results from deboning experiments using a prototype system developed to perform bird shoulder cuts are reported.