Edmund Biden

Gait laboratory analysis of a posterior cruciate-sparing total knee arthroplasty in stair ascent and descent.

Successful posterior cruciate ligament-sparing total knee arthroplasty functions in an equivalent fashion to a contralateral normal limb during the mechanical stresses of stair ascent and descent. Motion and force plate analysis reveal highly symmetric gait patterns. Sagittal angles are greater than previously reported for the total condylar prosthesis and are nearly equal to those recorded for the age-matched normal population.

An index to quantify normality of gait in young children.

Gait patterns are often described by recording the changes in angular rotation of such joints as the hip, knee and ankle, during a complete cycle. Each joint exhibits distinctive behavior throughout the gait cycle, and abnormal gait can be described by measuring departure from a typical (mean) joint rotation curve. Standard techniques for observation of gait patterns produce large sets of data. Data reduction is achieved in this work by locating primary directions of variation from mean behavior. Variation from the mean can then be summarized with a one-dimensional statistic, thought of as a squared distance from the population mean. Percentiles of this one-dimensional index can be calculated, enabling classification of a child as normal, unusual or abnormal. A key feature of this analysis is that it is applied across multiple joint angle curves and their derivatives, thus providing a measure that takes account of the interactions between the curves as well as their individual characteristics. A data base of 348 gait cycles, collected from normal children, aged 3-7, were analyzed. Data on each child were stored in a 36-dimensional vector. Most information on patterns of variation among normal children can be stored in a smaller 11-dimensional vector, which can be used for diagnostic purposes. Performance of the one-dimensional index of gait is demonstrated on data from very young children, and on children, up to age 7, who were born prematurely.

Effect of stiffness and movement speed on selected dynamic torque characteristics of hydraulic-actuation joystick controls for heavy vehicles

The purpose of this work was to quantify the effects of joystick stiffness and movement speed on the dynamic torque characteristics of hydraulic-actuation joystick controls, as found in off-road vehicles, as one of the initial steps towards the development of a joystick design protocol. Using a previously developed mathematical model in which a hydraulic-actuation joystick is assumed to rotate about two axes where the rotation origin is a universal joint, the dynamic torque characteristics incurred by an operator were predicted. Utilizing a laboratory mock-up of an excavator cab environment, three actuation torque characteristics (peak torque, angular impulse and deceleration at the hard endpoint) were quantified for nine unskilled joystick operators during the use of a commonly used North American hydraulic-actuation joystick. The six different experimental conditions included combinations of three joystick stiffnesses and two movement speeds. The highest instantaneous input torque over the course of the joystick movement (not including the hard endpoint) was evaluated using the peak torque value. Angular impulse provided an indication of the sustained exposure to force. The third indicator, deceleration at the hard endpoint, was included to provide a description of impact loading on the hand as the joystick came to a sudden stop. The most important result of this work is that the dynamic torque characteristics incurred during hydraulic-actuation joystick use are substantial. While the peak torque values were not very different between the fast and slow motion conditions, the high decelerations even for slow movements observed at maximum excursion of the joystick indicate that the dynamics do matter. On the basis of deceleration at the hard endpoint and peak torque, the joystick movements that require the highest values for a combination of torque variables are the side-to-side ones. This suggests that less stiff balance and return springs should be considered for these directions than for forward and backward movements. However, if the design does not minimize acceleration, it is important that the spring stiffness not be too low since deceleration at the joystick hard endpoint will be very high causing the operator to incur large palm and finger impacts.

Off-road machine controls: investigating the risk of carpal tunnel syndrome

Occupationally induced hand and wrist repetitive strain injuries (RSI) such as carpal tunnel syndrome (CTS) are a growing problem in North America. The purpose of this investigation was to apply a modification of the wrist flexion/extension models of Armstrong and Chaffin (1978, 1979) to determine if joystick controller use in oV-road machines could contribute to the development of CTS. A construction equipment cab in the laboratory was instrumented to allow force, displacement and angle measurements from 10 operators while they completed an ˜ 30-min joystick motion protocol. The investigation revealed that both the external fingertip and predicted internal wrist forces resulting from the use of these joysticks were very low, indicating that the CTS risk associated with this factor was slight. However, the results also indicated that, particularly for the ‘forward’ and ‘left’ right side motions and for all left side motions, force was exerted by other portions of the fingers and hand, thereby under-predicting the tendon tension and internal wrist forces. Wrist angles observed were highest for motions that moved the joysticks to the sides rather than front to back. Thus, the ‘right’ and ‘left’ motions for both hands posed a higher risk for CTS development. When the right hand moved into the ‘right’ position and the left hand moved into the ‘left’ position, the wrist went into extension in both cases. Results indicate that neither learning nor fatigue aVected the results.

Effect of joystick stiffness, movement speed and movement direction on joystick and upper limb kinematics when using hydraulic-actuation joystick controls in heavy vehicles

Despite the widespread use of hydraulic-actuation joysticks in mobile North American construction, mining and forestry vehicles, the biomechanical effects that joysticks have on their human operators has not been studied extensively. Using nine unskilled joystick operators and a laboratory mock-up with a commonly used North American heavy off-road equipment hydraulic-actuation joystick and operator seat, the purpose of this work was to quantify and compare the effects of three hydraulic-actuation joystick stiffnesses and two movement speeds on upper limb and joystick kinematics as one of the initial steps towards the development of a hydraulic-actuation joystick design protocol. In addition to providing a detailed description of the kinematics of a constrained occupational task, coupled with the corresponding effects of the task on operator upper limb kinematics, results from principal component analysis and ANOVA procedures revealed a number of differences in joystick and upper limb angle ranges and movement curve shapes resulting from the various joystick stiffness-speed combinations tested. For the most part, these joystick motion alterations were caused by small, insignificant changes in one or more upper limb joint angles. The two exceptions occurred for forward movements of the joystick; the fast speed – light stiffness condition movement pattern shape change was caused primarily by an alteration of the elbow flexion–extension movement pattern. Similarly, the fast speed – normal stiffness condition movement curve shape perturbation – was caused principally by a combination of significant movement curve shape alterations to elbow flexion–extension, external–internal shoulder rotation and flexion–extension of the shoulder. The finding that joystick stiffness and speed alterations affect joystick and upper limb kinematics minimally indicates that the joystick design approach of modelling the joystick and operator upper limb as a closed linkage system should be pursued. This approach would allow one to simulate the upper limb and joystick kinematics that result from virtual changes to upper limb and joystick lengths.

Comparison of two normative paediatric gait databases

The availability of age-matched normative data is an essential component of clinical gait analyses. Comparison of normative gait databases is difficult due to the high-dimensionality and temporal nature of the various gait waveforms. The purpose of this study was to provide a method of comparing the sagittal joint angle data between two normative databases. We compared a modern gait database to the historical San Diego database using statistical classifiers developed by Tingley et al. (2002). Gait data were recorded from 60 children aged 1–13 years. A six-camera Vicon 512 motion analysis system and two force plates were utilized to obtain temporal-spatial, kinematic, and kinetic parameters during walking. Differences between the two normative data sets were explored using the classifier index scores, and the mean and covariance structure of the joint angle data from each lab. Significant differences in sagittal angle data between the two databases were identified and attributed to technological advances and data processing techniques (data smoothing, sampling, and joint angle approximations). This work provides a simple method of database comparison using trainable statistical classifiers.

Bend-enhanced fiber optic sensors in a teleoperation application

Bend enhanced fiber (BEF) sensors are curvature-measuring optical analogs of elongation- measuring resistance strain gauges. They are made by treating optical fibers to have an optically absorptive zone along a thin axial stripe a few millimeters long. Light transmission through the fiber past this zone then becomes a robust function of curvature, three orders of magnitude more sensitive to bending than in the untreated fiber. Directionality and polarity of curvature are preserved in the light transmission function, over a linear range covering five orders of magnitude, centered about zero curvature. This paper describes a project in which BEF sensors were used to improve teleoperation of a small mobile robot, by instrumenting joint angles, an extension, and four forces. The operator, who formerly had only a televised view from a camera on the robot, now has additional information on a computer screen showing these parameters in graphical form. This information, provided entirely from fiber optic sensors, makes it considerably easier to manipulate the robot. The project also included demonstrations of a multiplexing system for larger BEF arrays, use of BEF sensors in prosthetics, and plasma enhanced chemical vapor deposition of a light absorptive coating on BEF sensors.

Design and development of ankle-foot prosthesis with delayed release of plantarflexion.

A computer-controlled mechanism that fits a standard ankle-foot prosthesis was designed to capture the absorbed energy in the ankle and delay its release until specific times in the gait cycle. This mechanism used a direct current motor to take up and hold the compression of a carbon-fiber ankle joint. Based on the timing of the contact forces between the foot and the ground, a microprocessor released the spring at preset times later in the gait cycle. This mechanism was added to a Talux prosthetic foot and was employed by a user of a conventional energy-storage ankle-foot prosthesis. His gait was recorded using a motion analysis system. Five settings: 0, 55, 65, 75, and 85 ms delay were tested on separate days, and the standard kinematic and kinetic gait data were recorded. The user reported some settings were more comfortable than others. When these preferences were tested with a randomized double-blind trial, the preferences were not consistent. A second user showed a preference for the 55 ms delay. The modifications to the device resulted in changes to the gait of the subjects, including increased cadence and kinematics of the unaffected joints and a longer, slower push from the ankle, which was noticed by both of the subjects.

Design of a compact, reconfigurable, prosthetic wrist

The design of a prosthetic wrist is the result of compromises between the function and the practicality of the device. Conventional prosthetic wrists use a single degree of freedom to produce pro/supination of the hand. It has not been demonstrated that this is the most functional alignment for a single axis. Previous work by the authors suggests that if the wrist must have only one rotatory axis then a more oblique orientation would be more functional. To test this idea, a compact wrist with a single axis and spherical design has been made that will allow any axis of rotation to be selected and the functional performance of the resulting arm be tested.

Application of time series and polynomial learning networks to robot trajectory error control

Abstract A compensatory control scheme based on measured errors at the end-effector is proposed using polynomial learning networks and time series modeling. Based on experimental data from an industrial manipulator programmed forms straight-line motion, trajectory deviations are modeled using both techniques. The performance of the models are compared at different locations in the workspace. It is shown that the robot arm signature can be obtained and that models from both techniques can be used to forecast trajectory errors. A method to implement the proposed scheme is also given.