Uri Tasch

The development of an objective lameness scoring system for dairy herds: Pilot study

Early detection of bovine lameness offers the potential for effective treatment and effectual management of hoof and leg ailments. This technical note examines statistical relationships between visually derived lameness scores and mechanically derived limb movement variables (LMVs) for sound and lame dairy cows. The visually derived lameness scores were based on observations of arched backs while cows stood and walked. The mechanically derived LMVs were captured as cows walked freely over a patent–pending force–plate system that generates signatures of ground reaction forces. A statistical model evaluated a lameness index (LI) using peak ground reaction force (PGRF). The LI allowed the 23 cows to be classified correctly according to their visually derived lameness scores, with three exceptions. This pilot study demonstrated that the outputs of our force–plate system can be used to relate lameness scores to measurable LMVs.

Enhancing the prediction accuracy of bovine lameness models through transformations of limb movement variables.

The issue of modeling bovine lameness was explored by testing the hypothesis that B-spline transformation of limb movement variables (LMV) employed in predictive models improved model accuracy. The objectives were to determine the effect of number of B-spline knots and the degree of the underlying polynomial approximation (degree of freedom) on model accuracy. Knot number used in B-spline transformation improved model accuracy by improving model specificity and to a lesser extent model sensitivity. Degree of polynomial approximation had no effect on model predictive accuracy from the data set of 261 cows. Model stability, defined as changes in predictive accuracy associated with the superimposition of perturbations (0.5 and 1.0%) in LMV on the measured data, was explored. Model specificity and to a lesser degree, sensitivity, increased with increased knot number across data set perturbations. Specificity and sensitivity increased by 43 and 11%, respectively, when knot number increased from 0 to 7 for a perturbation level of 0.5%. When the perturbation level was 1%, the corresponding increases in specificity and sensitivity were 32 and 4%, respectively. Nevertheless, different levels of LMV perturbation varied the optimal knot number associated with highest model accuracy. The optimal knot number for 0.5% perturbation was 8, whereas for 1% perturbation the optimal knot number was 7. The B-spline transformation improved specificity and sensitivity of predictive models for lameness, provided the appropriate number of knots was selected.

Toeard a formulation of the human grasping quality sense

This article examines the grasping quality problem and suggests a formulation that can capture the major mechanisms that generate the human grasping quality sense. Here, the quality of a grasp is examined from the gripper, object, and grasping-configuration perspectives. These perspectives are incorporated into the formulation by selecting an appropriate objective function that is minimized subject to constraints that represent the geometry, friction, and force-balance conditions of a grasp. The quality of a grasp is depicted as a polar plot that demonstrates the dependency of grasping quality on the external-loading direction. The suggested grasping quality measures possess characteristics that are in agreement with basic human intuition. In particular this article proves that the three proposed quality measures are improved when the number of contact points is increased. In summary, the suggested grasping quality formulation captures some of the physical mechanisms that characterize a human grasp, and therefore it may lead to a powerful mathematical model of the human grasping quality sense.

A two-DOF manipulator with adjustable compliance capabilities and comparison with the human finger

This article addresses compliance control issues and develops an actuator that modulates the stiffness and independently sets the angular positioning of a revolute joint. The capability to decouple the position from the compliance modulations is instrumental in a wide range of robotic contact operations. It is shown that a five input control scheme fully characterizes the position and compliance of a two-DOF manipulator. In an effort to characterize the control capabilities of a human finger, the compliance values of the proximal and middle joints are assessed experimentally. The results of the experiment show that a five input control is evidently within the human finger capabilities. In an effort to enhance the compliance capabilities of robotic systems, the authors believe that the newly developed actuation scheme will impact the automation of manufacturing tasks in which contact operations are inevitable.

Diversity in the magnitude of hind limb unloading occurs with similar forms of lameness in dairy cows

The objective of the study was to evaluate the relationship of veterinary clinical assessments of lameness to probability estimates of lameness predicted from vertical kinetic measures. We hypothesized that algorithm-derived probability estimates of lameness would accurately reflect vertical measures in lame limbs even though vertical changes may not inevitably occur in all lameness. Kinetic data were collected from sound (n=179) and unilaterally lame (n=167) dairy cattle with a 1-dimensional, parallel force plate system that registered vertical ground reaction force signatures of all four limbs as cows freely exited the milking parlour. Locomotion was scored for each hind limb using a 1-5 locomotion score system (1=sound, 5=severely lame). Pain response in the interdigital space was quantified with an algometer and pain response in the claw was quantified with a hoof tester fitted with a pressure gage. Lesions were assigned severity scores (1=minimal pathology to 5=severe pathology). Lameness diminished the magnitude of peak ground reaction forces, average ground reaction forces, Fourier transformed ground reaction forces, stance times and vertical impulses in the lame limbs of unilaterally lame cows. The only effect of lameness on the opposite sound limb was increased magnitude of stance times and vertical impulses in unilaterally lame cows. Symmetry measures of the peak ground reaction forces, average ground reaction forces, Fourier transformed ground reaction forces, stance times and vertical impulses between the left and right hind limbs were also affected in unilateral lameness. Paradoxically, limbs with clinically similar lesion and locomotion scores and pain responses were associated with a broad range of load-transfer off the limb. Substantial unloading and changes in the vertical limb variables occurred in some lameness while minimal unloading and changes in vertical limb variables occurred in other lameness. Corresponding probability estimates of lameness accurately reflected changes in the vertical parameters of limbs and generated low probability estimates of lameness when minimal unloading occurred. Failure to transfer load off limbs with pain reactions, locomotion abnormalities and lesions explained much of the limited sensitivity in lameness detection with vertical limb variables.

Measuring early pre-symptomatic changes in locomotion of SOD1-G93A rats—A rodent model of amyotrophic lateral sclerosis

A locomotion analysis system for laboratory rats is presented. The system produces locomotion parameters (LPs) in 4 different domains: force, space, time and frequency. Video images of the walking rats are used to associate the system signals with individual limbs. Numerous LPs can be derived for every test run when the rat walks through the system on the way to sweets and a personal toy placed at the exit. This manuscript demonstrates that in order to differentiate SOD1-G93A mutant rat, a model of amyotrophic lateral sclerosis (ALS), from a Sprague Dawley (SD) control rat at a pre-symptomatic stage, one has only to use 8 key parameters. These 8 parameters are the bio-markers of ALS. The spline-based transformed values of these parameters are used as explanatory variables of a logistic regression model. This model predicts the probability that the examined rat belongs to the SOD1-G93A group. The model differentiates faultlessly between the SOD1 and control groups from the very first time the rats walked through the system at 51 days old. This system provides a new paradigm for ALS diagnosis, and it can have a significant impact on the development of new therapeutic procedures for ALS. The methodology presented in this manuscript can further address the development and validation of therapeutic procedures for other neurological diseases that affect locomotion.

A new representation for a robot grasping quality measure

When an object is held by a multi-fingered hand, the values of the contact forces can be multivalued. An objective function, when used in conjunction with the frictional and geometric constraints of the grasp, can however, give a unique set of finger force values. The selection of the objective function in determining the finger forces is dependent on the type of grasp required, the material properties of the object, and the limitations of the robot fingers. In this paper several optimization functions are studied and their merits highlighted. The paper introduces a graphical representation of the finger force values and the objective functions that enable one to select and compare various grasping configurations. The impending motion of the object at different torque and finger force values are determined by observing the normalized coefficient of friction plots

Gait analysis of locomotory impairment in rats before and after neuromuscular injury

We used a gait analysis system (GAS) to measure the changes in locomotion parameters of adult Sprague-Dawley rats after neuromuscular injury, induced by repeated large-strain lengthening contractions of the dorsiflexors muscles. We developed a logistic regression model from test runs of control and permanently impaired (denervation of the dorsiflexor muscles) rats and used this model to predict the probabilities of locomotory impairment in rats injured by lengthening contractions. The data showed that GAS predicts the probability of locomotory impairment with very high reliability, with values close to 100% immediately after injury and close to 0% after several weeks of recovery from injury. The six transformed locomotion parameters most effective in the model were in three domains: frequency, force, and time. We conclude that application of the GAS instrument with our predictive model accurately identifies locomotory changes due to neuromuscular deficits. Use of this technology should be valuable for monitoring the progression of a neuromuscular disease and the effects of therapeutic interventions.

THEORETICAL ANALYSIS OF STABILITY OF AXIALLY SYMMETRIC ROTATING OBJECTS WITH REGARD TO ORIENTING APPLES

Inspection using machine vision offers the potential for improved food safety and quality. However, effectiveness of fruit inspection has been limited by the difficulty of appropriately orienting fruit for imaging. Commercial orientation systems have had limited impact due to mechanical complexity, cost, error, or some combination thereof. Preliminary tests demonstrated that apples could be oriented by rolling them down a track consisting of two parallel rails. After achieving sufficient angular velocity, the apples moved to an orientation where the stem/calyx axis was perpendicular to the direction of travel and parallel to the plane of the track. The purpose of the current study was to examine whether this orientation phenomenon could be explained in terms of the inertial characteristics of axially symmetric objects. Rotation of a free body around an axis of axial symmetry was found to be stable, while rotation around an axis perpendicular to this symmetric axis was not. Furthermore, comparisons of action values for two different mathematical models of apples indicate that inertial characteristics can be used to orient apples. The critical assumption for this analysis was that for the same object traveling the same path with different initial orientations, lower action values represent preferred motions. This study introduces the novel use of action integrals to examine stability, and the results provide testable predictions that round apples as compared to elongated or squat apples and larger elongated apples will need to travel farther before orientation is favored.

Locomotion analysis of Sprague–Dawley rats before and after injecting 6-OHDA

The hypothesis that changes in measured ground reaction forces and time parameters during locomotion can noninvasively detect Parkinsonism in unilateral 6-OH dopamine (6-OHDA) lesioned rats is tested. It was found that changes of seven locomotion parameters can be used to construct a logistic regression model with a detection sensitivity and specificity of over 90% as compared to non-lesioned rats. Comparisons between this model and other neurological and neuromuscular disorders are presented.