Remote robot manipulator coupled with remote-controlled guide vehicle for soil sampling in hazardous waste sites

The important initial step for remediation of hazardous waste is contaminant analysis since the cleanup operation can not begin until the contaminants in hazardous waste sites have been clearly identified. Ames Laboratory, one of the U.S. Department of Energy sites, has developed a robotic sampling system for automation of real-time contaminant analysis in situ which will provide the advantage of lowering the cost per sample, eliminating personnel exposure to hazardous environments, and allowing quicker results. Successful accomplishment of real-time contaminant analysis will require a remote manipulator to perform the sampling tasks in remote and unstructured surroundings, and a remote-controlled guide vehicle to move a remote manipulator into the desired sampling location;This thesis focuses on the design and construction of a remote-controlled guide vehicle to move the robotic sampling system into the contaminated field to obtain soil samples at the desired locations, the development of an integrated dynamic model of a remote manipulator, the identification of dynamic parameters in the integrated dynamic model, and the design of a mobile robotic sampling system. A four-wheeled vehicle prototype has been constructed and its performance tested manually in the field to verify the design requirements. To remotely control the vehicle, mechanical requirements to activate the brake, throttle, transmission, and steering linkages were determined based on experimental results. A teleoperated control utilizing hundred feet long umbilical cords was first employed to remotely control the vehicle. Next, the vehicle was modified to remotely operate in the field by radio control without the aid of long umbilical cords, satisfying all the design specifications;To reduce modeling error in the robotic system, the integrated dynamic system comprised of a remote manipulator (located on a trailer pulled by the remote-controlled guide vehicle) and its drive system has been modeled. The friction model as a function of velocity is included. The dynamic parameters such as velocity-dependent friction and gravity torque in the integrated dynamic model have been determined based on experimental results;Finally, a robotic arm, a sampling tool, and a soil recovery fixture for a mobile robotic sampling system to be mounted on the remote-controlled guide vehicle have been designed and analyzed. The integrated dynamic model for the robotic arm (mounted on the remote-controlled guide vehicle) and its drive system has also been developed

Modeling of precision motion control systems: a relay feedback approach

Ph.DDOCTOR OF PHILOSOPH

Modeling of Force and Motion Transmission in Tendon-Driven Surgical Robots

Tendon-based transmission is a common approach for transferring motion and forces in surgical robots. In spite of design simplicity and compactness that comes with the tendon drives, there exists a number of issues associated with the tendon-based transmission. In particular, the elasticity of the tendons and the frictional interaction between the tendon and the routing result in substantially nonlinear behavior. Also, in surgical applications, the distal joints of the robot and instruments cannot be sensorized in most cases due to technical limitations. Therefore, direct measurement of forces and use of feedback motion/force control for compensation of uncertainties in tendon-based motion and force transmission are not possible. However, force/motion estimation and control in tendon-based robots are important in view of the need for haptic feedback in robotic surgery and growing interest in automatizing common surgical tasks. One possible solution to the above-described problem is the development of mathematical models for tendon-based force and motion transmission that can be used for estimation and control purposes. This thesis provides analysis of force and motion transmission in tendon-pulley based surgical robots and addresses various aspects of the transmission modeling problem. Due to similarities between the quasi-static hysteretic behavior of a tendon-pulley based da Vinci® instrument and that of a typical tendon-sheath mechanism, a distributed friction approach for modeling the force transmission in the instrument is developed. The approach is extended to derive a formula for the apparent stiffness of the instrument. Consequently, a method is developed that uses the formula for apparent stiffness of the instrument to determine the stiffness distribution of the tissue palpated. The force transmission hysteresis is further investigated from a phenomenological point of view. It is shown that a classic Preisach hysteresis model can accurately describe the quasi-static input-output force transmission behavior of the da Vinci® instrument. Also, in order to describe the distributed friction effect in tendon-pulley mechanisms, the creep theory from belt mechanics is adopted for the robotic applications. As a result, a novel motion transmission model is suggested for tendon-pulley mechanisms. The developed model is of pseudo-kinematic type as it relates the output displacement to both the input displacement and the input force. The model is subsequently used for position control of the tip of the instrument. Furthermore, the proposed pseudo-kinematic model is extended to compensate for the coupled-hysteresis effect in a multi-DOF motion. A dynamic transmission model is also suggested that describes system’s response to high frequency inputs. Finally, the proposed motion transmission model was used for modeling of the backlash-like hysteresis in RAVEN II surgical robot

Passenger Car Active Braking System: Model and experimental validation (Part I)

This paper introduces a method to characterize the dynamic behavior of a normal production hydraulic brake system through experiments on a hardware-in-the-loop test bench for both modeling (part I) and control (part II) tasks. The activity is relative to the analysis, modeling, and control of anti-lock braking system and electronic stability control digital valves, and is aimed at obtaining reference tracking and disturbance-rejection performance similar to that achievable when using pressure proportional valves. The first part of this two-part study is focused on the development of a mathematical model that emulates the pressure dynamics inside a brake caliper when the inlet valve, outlet valve, and motor pump are controlled by digital or pulse width modulated signals. The model takes into account some inherent nonlinearities of these systems, e.g. the variation of fluid bulk modulus with pressure, while inlet and outlet valves together with the relay box are modeled as second-order systems with variable gains. The hardware-in-the-loop test rig is used for both parameter estimation and model validation; the parameters and model will be used for the control strategy development presented in the second part of this study

Hybrid modeling and control of mechatronic systems using a piecewise affine dynamics approach

This thesis investigates the topic of modeling and control of PWA systems based on two experimental cases of an electrical and hydraulic nature with varying complexity that were also built, instrumented and evaluated. A full-order model has been created for both systems, including all dominant system dynamics and non-linearities. The unknown parameters and characteristics have been identi ed via an extensive parameter identi cation. In the following, the non-linear characteristics are linearized at several points, resulting in PWA models for each respective setup. Regarding the closed loop control of the generated models and corresponding experimental setups, a linear control structure comprised of integral error, feed-forward and state-feedback control has been used. Additionally, the hydraulic setup has been controlled in an autonomous hybrid position/force control mode, resulting in a switched system with each mode's dynamics being de ned by the previously derived PWA-based model in combination with the control structure and respective mode-dependent controller gains. The autonomous switch between control modes has been de ned by a switching event capable of consistently switching between modes in a deterministic manner despite the noise-a icted measurements. Several methods were used to obtain suitable controller gains, including optimization routines and pole placement. Validation of the system's fast and accurate response was obtained through simulations and experimental evaluation. The controlled system's local stability was proven for regions in state-space associated with operational points by using pole-zero analysis. The stability of the hybrid control approach was proven by using multiple Lyapunov functions for the investigated test scenarios.publishedVersio

Error modeling of precision orientation sensors in a fixed base simulation

Models of noise and dynamic characteristics of gyro and autocollimator for very small signal levels are presented. Measurements were evaluated using spectral techniques for identifying noise from base motion. The experiment was constructed to measure the precession, due to relativistic effects, of an extremely precise earth-orbiting gyroscope. The design goal for nonrelativistic gyro drift is 0.001 arcsec per year. An analogous fixed base simulator was used in developing methods of instrument error modeling and performance evaluation applicable to the relativity experiment sensors and other precision pointing instruments. Analysis of autocollimator spectra uncovered the presence of a platform gimbal resonance. The source of resonance was isolated to gimbal bearing elastic restraint properties most apparent at very small levels of motion. A model of these properties which include both elastic and coulomb friction characteristics is discussed, and a describing function developed

Nonlinear control of an industrial robot

The precise control of a robot manipulator travelling at high speed constitutes a major research challenge. This is due to the nonlinear nature of the dynamics of the arm which make many traditional, linear control methodologies inappropriate. An alternative approach is to adopt controllers which are themselves nonlinear. Variable structure control systems provide the possibility of imposing dynamic characteristics upon a poorly modelled and time varying system by means of a discontinuous control signal. The basic algorithm overcomes some nonlinear effects but is sensitive to Coulomb friction andactuator saturation. By augmenting this controller with compensation terms, these effects may largely be eliminated.In order to investigate these ideas, a number of variable structure control systems ~re applied to a low cost industrial robot having a highly nonlinear and flexible drive system. By a combination of hardware enhancements and control system developments, an improvement in speed by a factor of approximately three was achieved while the trajectory tracking accuracy was improved by a factor of ten, compared with the manufacturer's control system.In order to achieve these improvements, it was necessary to develop a dynamic model of the arm including the effects of drive system flexibility and nonlinearities. The development of this model is reported in this thesis, as is work carried out on a comparison of numerical algorithms for the solution of differential equations with discontinuous right hand sides, required in the computer aided design of variable structure control systems

Nonlinear dynamics of two angles subtended by an angle

The work was based from previous analytical results that aims to facilitate rotations. It aims to initially use an elliptical track. However, from previous experimental observations, it was noted that addition of another pendulum, at an angle, instead of introducing a circular track, seemed more effective in inducing rotations. The idea of inducing rotations with a higher range of frequency is intriguing, with rotations being one of the centerpiece of energy generations or mechanical motion. Rotations are used because there is a continuous translational energy as compared to oscillations where it loses energy on it’s peak. If the experiment can induce rotations with impacts present and is still capable of rotating to generate electricity, it could lead to many more possibilities. Renewable energy using vibration is the main approach of this work, and investigating ways to achieve such energy with rotations using electromechanical device is one of the initial conditions that have been chosen to act as a motivation

Modeling and control of a pneumatic muscle actuator

This thesis presents the theoretical and experimental study of pneumatic servo position control systems based on pneumatic muscle actuators (PMAs). Pneumatic muscle is a novel type of actuator which has been developed to address the control and compliance issues of conventional cylindrical actuators. Compared to industrial pneumatic cylinders, muscle actuators have many ideal properties for robotic applications providing an interesting alternative for many advanced applications. However, the disadvantage is that muscle actuators are highly nonlinear making accurate control a real challenge. Traditionally, servo-pneumatic systems use relatively expensive servo or proportional valve for controlling the mass flow rate of the actuator. This has inspired the research of using on/off valves instead of servo valves providing a low-cost option for servo-pneumatic systems. A pulse width modulation (PWM) technique, where the mass flow is provided in discrete packets of air, enables the use of similar control approaches as with servo valves. Although, the on/off valve based servo-pneumatics has shown its potential, it still lacks of analytical methods for control design and system analysis. In addition, the literature still lacks of studies where the performance characteristics of on/off valve controlled pneumatic systems are clearly compared with servo valve approaches. The focus of this thesis has been on modeling and control of the pneumatic muscle actuator with PWM on/off valves. First, the modeling of pneumatic muscle actuator system controlled by a single on/off valve is presented. The majority of the effort focused on the modeling of muscle actuator nonlinear force characteristics and valve mass flow rate modeling. A novel force model was developed and valve flow model for both simulation and control design were identified and presented. The derived system models (linear and nonlinear), were used for both control design and utilized also in simulation based system analysis. Due to highly nonlinear characteristics and uncertainties of the system, a sliding mode control (SMC) was chosen for a control law. SMC strategy has been proven to be an efficient and robust control strategy for highly nonlinear pneumatic actuator applications. Different variations of sliding mode control, SMC with linear model (SMCL) and nonlinear model (SMCNL) as well as SMC with integral sliding surface (SMCI) were compared with a traditional proportional plus velocity plus acceleration control with feed-forward (PVA+FF) compensation. Also, the effects of PWM frequency on the system performance were studied. Different valve configurations, single 3/2, dual 2/2, and servo valve, for controlling a single muscle actuator system were studied. System models for each case were formulated in a manner to have a direct comparison of the configuration and enabling the use of same sliding mode control design. The analysis of performance included the sinusoidal tracking precision and robustness to parameter variations and external disturbances. In a similar manner, a comparison of muscle actuators in an opposing pair configuration controlled by four 2/2 valves and servo valve was executed. Finally, a comparison of a position servo realized with pneumatic muscle actuators to the one realized with traditional cylinder was presented. In these cases, servo valve with SMC and SMCI were used to control the systems. The analysis of performance included steady-state error in point-to-point positioning, the RMSE of sinusoidal tracking precision, and robustness to parameter variations