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Lack of clean water in small remote communities in the developing world is a major health problem. Water purification and desalination systems powered by solar energy, such as photovoltaic powered reverse osmosis systems (PVRO), are potential solutions to the clean water problems in these small communities. PVRO systems have been proposed for various locations. However, small PVRO systems with production on the order of 1 m3/day for remote communities present some unique technical, cost and operational problems. This paper reports on a project in which a PVRO system is designed, fabricated and deployed in remote village in the Yucatan Peninsula of Mexico. The community residents are indigenous people who are subsistence farmers and beekeepers. Technical and economic models used to configure the system for the community are presented. A plan is developed in cooperation with the community aimed at making the system self-sustaining in the long term. Methods and materials are developed to permit the community members to operate and maintain the system themselves. The results provide insights for the design and deployment of small community-scale PVRO systems in remote communities.

Autonomous space robots will be required for such future missions as the construction of large space structures and repairing disabled satellites. These robots will need to be precisely controlled. However, factors such as manipulator joint/actuator friction and spacecraft attitude control thruster inaccuracies can substantially degrade control system performance. Sensor-based control algorithms can be used to mitigate the effects of actuator error, but sensors can add substantially to a space system’s weight, complexity, and cost, and reduce its reliability. Here, a method is presented to determine the sensor architecture that uses the minimum number of sensors that can simultaneously compensate for errors and disturbance in a space robot’s manipulator joint actuators, spacecraft thrusters, and reaction wheels. The placement and minimal number of sensors is determined by analytically structuring the system into “canonical chains” that consist of the manipulator links and spacecraft with force/torque sensors placed between the space robot’s spacecraft and its manipulators. These chains are combined to determine the number of sensors needed for the entire system. Examples of one- and two-manipulator space robots are studied and the results are validated by simulation.

Photovoltaic-powered reverse osmosis (PV/RO) is a practical method for desalinating water, especially for many small, remote, off-grid communities. It is shown here that thermal control can increase its productivity, making it more economically attractive. A solar panel produces more power at lower cell temperatures and an RO unit produces more fresh water for a given power with increasing water temperature. These complementary behaviors are exploited by cooling the solar panel using the RO feed water, which warms the water. Cooling the solar panel also permits the use of concentrating mirrors, which further increases system production. The control must also prevent overheating of the panel and the RO unit, and to balance the pressures in the system. Here, a controller is designed to meet these objectives. The effectiveness of controller design is verified in simulation and experiment.

Large parabolic dish concentrator mirrors are an important component of many solar energy systems. They need to be relatively precise and are expensive to fabricate and to transport. Here, a new concept for designing and fabricating large parabolic dish mirrors is presented. The dish mirror is formed from several optimal-shaped thin flat metal petals with highly reflective surfaces. Attached to the rear surface of the mirror petals are several thin layers whose shapes are optimized to have reflective petals form into a parabola when their ends are pulled toward each other by cables or rods. An analytical model to optimize the shape and thickness of the petals is presented. The validity of the concept is demonstrated using Finite Element Analysis and laboratory experiments. The concept would permit flat mirror elements to be easily fabricated and efficiently packaged for shipping to field sites where they can be assembled into the parabolic dish concentrators. The concept has the potential to provide precision solar parabolic solar collectors at a substantially lower cost than conventional methods.

Dielectric Elastomer Actuators (DEAs) show promise for robotics and mechatronics applications. They are lightweight, low costs, and have shown good performance in laboratory demonstration. However, these actuators have not been widely applied commercially after more than 10 years of development. One reason is that the mechanisms governing their performance are not completely understood. Hence designing practical actuators is difficult. This paper has the objective of understanding the dominant performance mechanisms of DEAs made with VHB 4905/4910 from 3 M. To do so, an experimental characterization of actuator performance is conducted in terms of force, power, current consumption, work output, and efficiency. Key performance mechanisms of viscoelasticity and current leakage are identified from experimental observations and analytical models are developed. The models explain well the experimental observations and should aid designers in selecting applications that are appropriate for DEAs as well as designing effective DEAs.

Dielectric elastomer actuators (DEA) have been studied extensively under laboratory conditions where they have shown promising performance. However, in practical applications, they have not achieved their full potential. Here, the results of detailed analytical and experimental studies of the failure modes and performance boundaries of DEAs are codified into design principles for these actuators. Analysis shows that the performance of DEAs made with highly viscoelastic polymer films is governed by four key mechanisms: pull-in failure, dielectric strength failure, viscoelasticity and current leakage. Design maps showing the effect of these four mechanisms on performance under varying working conditions are proposed. This study shows that the viscous nature of DEA is very important in their performance/reliability trade-offs. A proper balance of performance and reliability is key to successful design of DEAs.

Dielectric elastomer actuators (DEAs) show promise for robotic and mechatronic applications. However, to date, these actuators have experienced high rates of failure that have prevented their practical application. Here, large scale modes of failure of DEAs and their performance limits are studied. The objective is to provide design guidelines and bound the performance of DEAs that avoid failure. An idealized DEA is modeled and its failure is predicted as a function of film pre-stretch used during actuator fabrication, actuation voltage, and stretch rate. Three failure modes are considered: pull-in, dielectric strength, and material strength. Each failure mode is shown to dominate for different combinations of pre-stretch and stretch rate. High stretch rates lead to dielectric strength failure while low stretch rates lead to pull-in failure. Material strength failure is less important for most cases. Model predictions are validated experimentally using practical DEAs operating under load. This study suggests that DEAs cannot be operated reliably under load for long periods of time or low stretch rates due to pull-in failure limitations. To be reliable, DEAs must be used for short periods of time with high stretch rates.

Future space applications will require robotic systems to assemble, inspect, and maintain large space structures in orbit. For effective planning and control, robots will need to know the deformation and vibration of the structures with which they interact. This paper presents a method for estimating the shape, motion, and dynamic model parameters of a vibrating space structure using range imaging sensors. The method assumes that the mode shapes are approximately known a priori. An unscented Kalman filter exploits a mechanics-based dynamic model to extract the modal frequencies and damping as well as the modal coefficients and their time rate of change. Both asynchronous-capture (raster-scanning) and synchronous-capture sensors are treated. Theoretical development and experimental results using emulated space hardware are presented.

Binary actuation has been proposed to reduce complexity in robotic and mechatronic systems. However, a relatively large number of binary actuators are required to achieve the accuracy necessary for practical applications. Conventional actuators are not practical for such large degree-of-freedom (DoF) devices. Here, a dielectric elastomer (DE) actuator is developed for these applications. It is shown that DE actuators have high energy densities, light weight, low cost, and large displacements. Hence they could potentially make large DoF binary systems practical. DE actuators proposed here consist of thin electrically sensitive elastomer films that are mounted in a flexible frame that incorporates a passive bistable element. The frame prestrains the film and provides a restoring force that allows the actuator to operate bidirectionally. A simple experimental prototype 6-DoF binary manipulator demonstrates the concept

Important robotic tasks could be effectively performed by powerful and accurate manipulators. However, high accuracy is generally difficult to obtain in large manipulators capable of producing high forces due to system elastic and geometric distortions. In this work, a high-accuracy patient positioning system is calibrated, consisting of a six degree of freedom manipulator used to position cancer patients during proton therapy sessions. It is found that the original manipulator does not meet the required absolute accuracy due to both geometric and elastic deformation positioning errors. The experimentally identified errors are used to predict, and compensate for, end-point errors as a function of configuration and measured forces, improving the system absolute accuracy. Experimental results show that the adopted methodology is able to effectively correct for the system errors.

In field environments it is often not possible to provide robot teams with detailed a priori environment and task models. In such unstructured environments, robots will need to create a dimensionally accurate three-dimensional geometric model of its surroundings by performing appropriate sensor actions. However, uncertainties in robot locations and sensing limitations/occlusions make this difficult. A new algorithm, based on iterative sensor planning and sensor redundancy, is proposed to build a geometrically consistent dimensional map of the environment for mobile robots that have articulated sensors. The aim is to acquire new information that leads to more detailed and complete knowledge of the environment. The robot(s) is controlled to maximize geometric knowledge gained of its environment using an evaluation function based on Shannon’s information theory. Using the measured and Markovian predictions of the unknown environment, an information theory based metric is maximized to determine a robotic agent’s next best view (NBV) of the environment. Data collected at this NBV pose are fused using a Kalman filter statistical uncertainty model to the measured environment map. The process continues until the environment mapping process is complete. The work is unique in the application of information theory to enhance the performance of environment sensing robot agents. It may be used by multiple distributed and decentralized sensing agents for efficient and accurate cooperative environment modeling. The algorithm makes no assumptions of the environment structure. Hence, it is robust to robot failure since the environment model being built is not dependent on any single agent frame, but is set in an absolute reference frame. It accounts for sensing uncertainty, robot motion uncertainty, environment model uncertainty and other critical parameters. It allows for regions of higher interest receiving greater attention by the agents. This algorithm is particularly well suited to unstructured environments, where sensor uncertainty and occlusions are significant. Simulations and experiments show the effectiveness of this algorithm.

A simplified, closed-form version of the basic mechanics of a driven rigid wheel on low-cohesion deformable terrain is presented. This approach allows the formulation of an on-line terrain parameter estimation algorithm, which has important applications for planetary exploration rovers. Analytical comparisons of the original and simplified equations are presented, and are shown to closely agree. Experimental results from a single-wheel testbed operating in dry sand shows that the simplified equations can be used for mobility prediction with good accuracy. Methods for incorporating the simplified equations into an on-line terrain parameter algorithm are discussed.

Mobile robots are being developed for high-risk missions in rough terrain situations, such as planetary exploration. Here, a rough-terrain control methodology is presented that exploits the actuator redundancy found in multiwheeled mobile robot systems to improve ground traction and reduce power consumption. The algorithm optimizes individual wheel torque based on multiple optimization criteria, which are a function of the local terrain profile. A key element of the method is to be able to include estimates of wheel-terrain contact angles and soil characteristics. A method using an extended Kalman filter is presented for estimating these angles using simple on-board sensors. Simulation and experimental results for a micro-rover traversing challenging terrain demonstrate the effectiveness of the algorithm.

This paper presents the design of a new lightweight, hyper-redundant, deployable Binary Robotic Articulated Intelligent Device (BRAID), for space robotic systems. The BRAID is intended to meet the challenges of future space robotic systems that need to perform more complex tasks than are currently feasible. It is lightweight, has a high degree of freedom, and has a large workspace. The device is based on embedded muscle type binary actuators and flexure linkages. Such a system may be used for a wide range of tasks, and requires minimal control computation and power resources.@DOI: 10.1115/1.1637647#

A methodology for predicting noise and vibration of machines and their support structures is presented. Included is a heuristic energy-based criterion to assess the importance of dynamic coupling between a mechanism and its support structure based on a simplified analysis of a mechanism operating on a rigid base, which neglects the coupling. Also included is an analysis method that considers the coupling and to be used when the criterion reveals important coupling. The methodology is implemented using highly idealized closed form and more elaborate numerical descriptions and is checked against vibration and sound measurements of a plate subjected to periodic impacts by balls and a beam that rattles within a clearance bearing. The energy-based criterion is found to indicate situations in which mechanism-support coupling affects noise radiation. In some cases the coupling is observed to significantly affect vibration and noise radiation of the support structure, while having a relatively minor effect on mechanism response. Both the simple closed form and numerical descriptions are found to predict noise trends due to variations in machine speed and bearing clearance, and the numerical descriptions more accurately predict overall and band levels of noise radiation.

Final program http://www.asmeconferences.org/IDETC2010/pdfs/IDETC2010FinalProgram.pdf lists this paper., Precision mirrors are required for effective solar energy collectors. Manufacturing such mirrors and making them robust to disturbances such as thermal gradients is expensive. In this paper, the use of parallel binary actuation to control the shape of mirrors for solar concentrators is explored. The approach embeds binary actuators in a compliant mirror substructure. Actuators are deployed in a specified pattern to correct the mirror shape. The analysis for binary-actuated compliant mirror structures is presented. Analytical models are developed for one-dimensional and two-dimensional compliant structures with embedded binary actuators. These analytical models are validated using finite element analysis and experimental studies. The models and experiments demonstrate the capabilities of binary actuated mirrors. System workspace is explored, the principle of superposition required for their control is demonstrated, as is the mirror ability to correct its figure., Northrop Grumman Corporation, Cyprus Institute

This paper describes a genetic algorithm planning method for autonomous robots in unstructured environments. It presents the approach and demonstrates its application to a laboratory planetary exploration problem. The method represents activities of the robot with discrete actions, or action modules. The action modules are assembled into an action plan with a Genetic Algorithm (GA). A successful plan allows the robot to complete the task without violating any physical constraints. Plans are developed that explicitly consider constraints such as power, actuator saturation, wheel slip, and vehicle stability. These are verified using analytical models of the robot and environment. The methodology is described in the context of planetary exploration similar to the NASA Mars Pathfinder mission. More aggressive missions are planned where rovers will explore scientifically important areas that are difficult to reach (e.g., ravines, craters, dry riverbeds, and steep cliffs). The proposed approach is designed for such areas.

The basic technology for a robotic system is developed to automate the packing of polycrystalline silicon nuggets into a fragile fused silica crucible in Czochralski (melt pulling) semiconductor wafer production. The highly irregular shapes of the nuggets and the packing constraints make this a difficult and challenging task. To address this task, key research areas are identified, developed, and integrated. In this system, nuggets are grasped by a three-cup suction gripper and manipulated with a seven-degree-of-freedom SCARA manipulator. An optical 3-D vision system, based on active laser triangulation, measures nugget and crucible profiles. A model-free Virtual Trial and Error packing algorithm determines optimal nugget placement in real time. A hybrid position-force control scheme has been implemented and tested for physical nugget placement. The simulation and laboratory tests show that the system has the capabilities of meeting high production rates, achieving high process constraints, and maintaining cost effectiveness that exceed levels obtained with manual packing. The results suggest that model-less robotic sensor control systems can be effective in manufacturing applications. The key contribution of this paper is to show that robot systems can be effectively used to manipulate highly irregular shaped objects in the context of real commercial manufacturing processes.

Systems such as electronics, cars, computers, and robots are assembled from modular components for specific applications. Photovoltaic reverse osmosis (PVRO) systems, which can be custom-tailored for the water demands and solar properties of particular communities, are an important potential application of modular systems. Clearly, to be financially viable, such systems must be assembled from commercially available components and subsystems (modules). Designing a system from modular components for a specific application is not simple. Even for a relatively small inventory of modular components, the number of possible system configurations that exist is extremely large. For a small community, determining the best system configuration is an overwhelming task due to lack of expertise. This paper presents a modular design architecture that can be implemented on a laptop so nonexperts can configure systems from modular components. The method uses a hierarchy of filters, which can be provided from an expert system, to limit the large design space. Optimization methods and detailed models are then used to configure the location-specific system from the reduced design space. The method is applied here to community-scale PVRO systems and example cases demonstrate the effectiveness of the approach.

Sun tracking heliostat mirrors are key components of many solar power systems. They must track the Sun’s position in the sky using a spatial 3-D robotic mount. In addition, their ideal shape is a section of a spatial paraboloid that changes as a function of time and the mirrors’ positions in the system. Errors in this shape results in reduced system efficiency. The practical implementation of such an ideal heliostat is very difficult and expensive. Here, a novel compliant heliostat design concept is proposed to solve this problem by simply applying moments to the corners of a flat plate whose elastic properties have been tailored to the heliostat’s position in the system. Analytical studies of concept are presented that show its performance closely approximates those produced by an ideal paraboloid and that are substantial improvements over current heliostats. Experimental results are presented to validate the approach.

A simplified Cartesian computed torque (SCCT) control scheme and its application to an experimental climbing robot named LIBRA is presented. SCCT control is developed exploiting some of the characteristics of highly geared mobile robots. The effectiveness of the method is shown by simulation and experimental results using the LIBRA robot. SCCT control is shown to have improved performance, over traditional Jacobian transpose control, for the LIBRA multilimbed robot. [S0022-0434(00)03501-2]

A radiation efficiency is developed for sound radiation from rectangular plates with unbaffled edges below the plate critical frequency. the expression modifies the modal average radiation efficiencies obtained from the simply supported plane-baffled plate by considering the effects of fluid flow around a structure. These flows reduce sound radiation by allowing fluid to escape compression.The unbaffled plate radiation efficiency is assessed by comparison with experimental data of sound radiated by impacts between balls and a plate. The expression is observed to be more accurate than the simply supported plane-baffled plate model and more versatile than a model of sound radiated from a plane-baffled free edge of a plate. Sound radiated by non-propagating plate vibration near ball-plate impacts appears to play a minor role. Improvements in accurate over the simply supported plane-baffled model typically range from 4–12 dB, with the greatest improvements occurring at low frequencies. A statistical method for bounding radiated sound power with a degree of confidence is also developed and tested against measured data. The results are encouraging but not statistically conclusive due to a limited amount of measured data.

In a Solar Power Tower (SPT) system, the ideal shape of a heliostat concentrator is a section of paraboloid which is a function of the location in the array and the incidence sun angle. This shape is difficult to achieve and limits the system efficiency. A shape-optimized compliant (SOC) design of parabolic heliostats is presented here to solve this problem. An approximation of the ideal shape is suggested to use an optimized stationary paraboloid shape which only varies with heliostat location in the array. A compliant structure design is proposed that to use a simple flat mirror with a two-dimensional tailored stiffness profile to form the required parabolic surface using adjustment mechanisms at each corner. This design is validated by numerical simulations including FEA tools, ray tracing, and classical nonlinear optimization. The annual performance shows that the SOC heliostat will substantially improve the efficiency and benefit the SPT system.

This research investigates using a manipulator to tactilely explore objects and environments when significant backlash affects its joint’s positions. A typical application is the exploration of rough environments, such as oil wells, where the harsh conditions dictate the use of tactile exploration. These conditions can result in large, unknown, and variable backlash in the manipulator’s transmissions, which strongly affects the measurement precision. Here, a method is developed to simultaneously map the unknown surface and identify the joint backlash. The robot probes the surface and uses its encoder readings to construct a partial map of the environment as a combination of geometric primitives. While the surface is built, the same data are also used to estimate backlash in the joints and to correct the surface measurements for backlash error. The effectiveness of the approach is demonstrated in simulation case studies and laboratory experiments.

A dynamic modeling method is presented for spatial elastic manipulators that can account for a number of their realistic properties, including bearing clearances, actuator dynamics, and control system characteristics. Forces in the bearing clearances are modeled by nonlinear functions of the links’ relative motions and the internal geometry of the connection, or by experimentally measured properties. A detailed model is given for a revolute connection with radial and axial clearances. Results obtained for a SCARA manipulator show that the combined dynamic effects of bearing clearances, link elasticity, and control system characteristics can significantly degrade the system’s performance.

Dynamic Singularities are shown for free-floating space manipulator systems where the spacecraft moves in response to manipulator motions without compensation from its attitude control system. At a dynamic singularity the manipulator is unable to move its end-effector in some inertial direction; thus dynamic singularities must be considered in the design, planning, and control of free-floating space manipulator systems. The existence and location of dynamic singularities cannot be predicted solely from the manipulator kinematic structure because they are functions of the dynamic properties of the system, unlike the singularities for fixed-base manipulators. Also analyzed are the implications of dynamic singularities to the nature of the system’s workspace.

Future robotic manipulator systems will be required to per form complex tasks in space such as satellite repair. These robotic manipulators will encounter a number of kinematic, dynamic, and control problems caused by the dynamic coup ling between the manipulators and its spacecraft. This dy namic coupling also makes it difficult to analyze these sys tems. This paper introduces a new analytical modeling method for space manipulators called the Virtual Manipula tor (VM), which has a fixed base in inertial space at a point called a Virtual Ground. The kinematics and dynamics of the manipulator, spacecraft, and payload can be described relatively easily in terms of the VM. With its fixed base, the Virtual Manipulator is shown to have the potential to be an effective aid for the analysis, design, and development of future space manipulator systems.

Fundamental studies of Dielectric Elastomer Actuators (DEAs) using viscoelastic materials such as VHB 4905/4910 from 3M showed significant advantages at high stretch rates. The film's viscous forces increase actuator life and the short power-on times minimize energy losses through current leakage. This paper presents a design paradigm that exploits these fundamental properties of DEAs called discrete actuation. Discrete actuation uses DEAs at high stretch rates to change the states of robotic or mechatronic systems in discrete steps. Each state of the system is stable and can be maintained without actuator power. Discrete actuation can be used in robotic and mechatronic applications such as manipulation and locomotion. The resolution of such systems increases with the number of discrete states, 10 to 100 being sufficient for many applications. An MRI-guided needle positioning device for cancer treatments and a space exploration robot using hopping for locomotion are presented as examples of this concept.

A thermal control architecture design study is conducted for a novel robotic planetary and lunar surface exploration concept. The concept is based on the deployment of a large number of small spherical mobile robots over large areas, which employ hopping, bouncing and rolling as means of locomotion. The aim of the research is to prevent freezing and overheating of the robots, without compromising their mechanical and thermal reliability and stability. The proposed thermal control architecture relies on a low emissive silver surface coating and a low conductive silica aerogel insulation layer. This enables a single design to be used for several important potential explorations. The effects of a thermal control heat rejection mechanism, composed of a variable emittance coating and heat switch, are also studied in order to increase mission flexibility.

Dielectric Elastomer (DE) actuators have been studied extensively under laboratory conditions where they have shown promising performance. However, in practical applications, they have not achieved their full potential. Here, the results of detailed analytical and experimental studies of the failure modes and performance boundaries of DE actuators are presented. The objective is to establish fundamental design principles for DE actuators. Analytical models suggest that DE actuators made with highly viscoelastic films are capable of reliably achieving large extensions when used at high speeds (high stretch rates). Experiments show that DE actuators used in low speed applications, such as slow continuous actuation, are subject to failure at substantially lower extensions and also have lower efficiencies. This creates an important reliability/performance trade-off because, due to their viscoelastic nature, highest DE actuators forces are obtained at low speeds. Hence, DE actuator design requires careful reliability/performance trade-offs because actuator speeds and extensions for optimal performance can significantly reduce actuator life.

An omni-directional mobility platform design concept using two active split offset castors (ASOC) and one or more conventional castors is presented. An ASOC module consists of two coaxial conventional wheels driven independently and connected to the platform via an offset link. The kinematics and implementation of the omni-directional platform is described and analyzed. Particular attention is paid to the system performance on uneven floors. The fundamental mechanics of the ASOC wheel scrubbing, which is critical to system wear and energy use, is analyzed and compared to conventional active castor designs. The effectiveness of the design is shown experimentally using an intelligent mobility aid for the elderly. @DOI: 10.1115/1.1767181#

Long reach manipulator systems (LRMS) can perform tasks in difficult to reach locations. They use a small and fast manipulator mounted on a large flexible structure that can vibrate, degrading the system performance. Control methods that use strain measurements of the flexible structure have been proposed to control the system’s position in spite of the supporting structure’s vibrations using a model of the structure that relates strains to displacements. Here the minimum number of strain sensors needed to accomplish this control and their optimal locations on the flexible supporting structure are determined. These locations have been selected to achieve high measurement resolution, to maximize the computational robustness and to minimize the error in the identification of the structure’s strain-displacement model. The results are validated with simulations and experiments using a six degree of freedom laboratory LRMS.

The results of experimental and analytical studies of the dynamic response of machines with flexible links and connection clearances are presented. These results suggest that the actual dynamic response of such systems inherently exhibits both a large amount of variability and high sensitivity to small parameter changes and operating conditions. This work suggests that the accuracy of the dynamic force predictions given by computer simulations for such systems is fundamentally limited, and therefore such simulations should be used in system design with care.

The basic technology for a robotic system is developed to automate the packing of polycrystalline silicon nuggets into fragile fused silica crucible in Czochralski (melt pulling) semiconductor wafer produc- tion. The highly irregular shapes of the nuggets and the packing con- straints make this a difficult and challenging task. It requires the delicate manipulation and packing of highly irregular polycrystalline silicon nug- gets into a fragile fused silica crucible. For this application, a dual optical 3-D surface mapping system that uses active laser triangulation has been developed and successfully tested. One part of the system mea- sures the geometry profile of a nugget being packed and the other the profile of the nuggets already in the crucible. A resolution of 1 mm with 15-KHz sampling frequency is achieved. Data from the system are used by the packing algorithm, which determines optimal nugget placement. The key contribution is to describe the design and implementation of an efficient and robust 3-D imaging system to map highly irregular shaped objects using conventional components in context of real commercial manufacturing processes. © 2002 Society of Photo-Optical Instrumentation Engi- neers. (DOI: 10.1117/1.1474438)

Important performance limitations in mechanical systems results from clearances which cause rapid wear, increased noise and vibration. Relatively little experimental investigation has been performed in this area, although a number of analytical studies have been carried out. Recent studies of the latter kind show the effect of clearances is to amplify, greatly, connection forces, and that the introduction of link flexibility tends to reduce these impact forces significantly. This study shows experimentally the validity of the analytical studies and the mitigating effects of link flexibility on impact forces.

The time domain behavior of nonlinear dynamic systems often is obtained by numerical integration on the digital computer. These solutions are usually expensive and limit the scope of the dynamic study. The proposed improved technique results in a substantial increase in the computational efficiency by using automatic symbolic manipulation to generate explicit equations of motion algebraically prior to numerical integration. A model is presented which considers the effects of the presence of time-invariant and time-varying symbolic terms and of the sparsity of system elements to provide analytical guidelines for the use of this technique. A number of case studies including typical computational costs are presented.

The digital computer is often used to perform time domain dynamic analyses of non-linear systems. Such analyses are notoriously expensive. In many cases this expense is due to algebraic computation with the solution process. Presented is a solution approach, using modern automatic symbolic manipulation techniques, which will result in substantial computational savings for a wide class of problems. Included are guidelines based on fundamental mathematical analysis, to predict which problems will benefit from this simulation approach.

The achievement of quality dynamic performance in manipulator systems is difficult using conventional control methods because of both the inherent geometric nonlinearities of these systems and the dependence of the system dynamics on the characteristics of manipulated objects. A model-referenced adaptive control law is developed for maintaining uniformly good performance over a wide range of motions and payloads. The effectiveness of the approach is demonstrated in several simulations and the system stability as a function of input is investigated. Also developed is a “learning signal” approach designed to minimize initial transients arising from abrupt changes in the inertial payload.

The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. The optimal open-loop torques are found, and a method is given for implementing these torques with a conventional linear feedback control system. The algorithm allows bounds on the torques that may be arbitrary functions of the joint angles and angular velocities. This method is valid for any path and orientation of the end- effector that is specified. The algorithm can be used for any manipulator that has rigid links, known dynamic equations of motion, and joint angles that can be determined at a given position on the path.