Transactions of the Canadian Society for Mechanical Engineering

Volume 35 (2011), Issue 2

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A multidisciplinary design optimization (MDO) approach is proposed to aid in the prediction of non-contact anterior cruciate ligament (ACL) injury mechanisms and risk factors. In this investigation the need for such an approach is argued based on an exhaustive evaluation of diverse factors that cause non-contact ACL injury, and the similarly numerous and different existing study approaches that have been carried out to investigate injury. The proposed MDO approach fuses patient data and existing study approaches via an artificial intelligent (AI) technique—absent in previous biomechanics investigations—so as to offer new insights into ACL injury prevention.

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This paper investigates the stator and the rotor vibration characteristics of turbo-generator under the air gap eccentricity fault. Firstly the air gap magnetic flux density of the fault is deduced, and the formula of the magnetic pull per unit area acting on the stator and the unbalanced magnetic pulls of x-axis and y-axis acting on the rotor are respectively gotten. Then the static eccentricity, the dynamic eccentricity and the mixed eccentricity are respectively studied to analyze the stator and the rotor vibration characteristics. Finally experiments are done on a SDF-9 non-salient fault simulating generator to verify the theoretical results. The investigation results of this paper will be beneficial to the air gap eccentricity fault diagnosis of turbo-generator.

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This paper presents results of evaluating different concepts of haptic and visual force feedback interfaces using a force-reflecting hand-controller designed to guide an ultrasound probe held by a robotic device. Experiments were conducted that resemble the type of path alignment and force regulating tasks that are needed to perform ultrasound examinations, remotely. In the first experiment, the effectiveness of visual force feedback, augmented haptic feedback and augmented haptic plus visual force feedback was tested. In the second experiment, the tasks were executed under communication network delays. The results confirm the expected observation that long variable communication delays degrade force regulating tasks using only the visual force feedback approach. The introduction of passive haptic feedback that constructs forces locally, allows participants to improve their performance, without causing instability due to variable or long network delays.

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Pose measurement is an important tool for robot calibration. This paper describes the development and implementation of a technique of camera-aided pose measurement, tested on the Planar Double Triangular Parallel Manipulator (PDTPM). A stationary camera is used to take photos of the End Effector (EE) where a certain array of Light Emitting Diodes (LED) is mounted on. Using various image processing techniques, the coordinates of the LEDs are registered in the image in order to derive the projection matrix that maps any point of the image plane to world coordinates in the EE moving plane. This homography is computed with a method where the vanishing line is treated as the principal component. This estimate is more robust and faster than the Direct Linear Transformation (DLT) method. It was shown that poses could be quickly registered at submillimetre precision notwithstanding inexpensive, relatively low resolution optics. The measurement system is easy to setup, portable, accurate, low cost and it is believed to be a valuable tool.

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A sufficient condition for exact linearization of a nonlinear system via an exponential transformation is obtained as a Lagrange partial differential equation. When its solution can be found, the transformation is determined such that the nonlinear systemis exactly converted into a linear system with arbitrary dynamics. When the transformation is invertible, this technique can be applied to exact discretization. Several examples are given to demonstrate the linearization and discretization processes and associated conditions. Asimulation result is presented to show that, under proper conditions, the obtained discrete-time model gives values that are identical to the continuous-time original at discrete-time instants for any sampling intervals.

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A two-dimensional Computational Fluid Dynamics (CFD) analysis of the Ahmed body is performed using the k-omega-SST turbulence model implemented in the OpenFOAM (OF) software. The analysis is then modified to include a rotating paddle wheel which captures energy from the swirl that forms behind the vehicle. The rotating wheel is implemented using a General Grid Interface (GGI) in the mesh. Flow energy is captured by the wheel and the power generated by the wheel reaches 16.1Wat optimal conditions. Overall drag reductions of up to 7.6% are also found as side-effects of the rotating paddle wheel. Computations are run in parallel on a dual core computer. A mesh of 30,000 cells is used. Y+ values on the walls of the vehicle range from 60 to 500. Tests are run at both fixed and variable paddle wheel angular velocities.

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An accelerometer-array calibration method is proposed in this paper by which we estimate not only the accelerometer offsets and scale factors, but also their sensitive directions and positions on a rigid body. These latter parameters are computed from the classical equations that describe the kinematics of rigid bodies, and by measuring the accelerometer-array displacements using a magnetic sensor. Unlike calibration schemes that were reported before, the one proposed here guarantees that the estimated accelerometer-array parameters are globally optimum in the least-squares sense. The calibration procedure is tested on OCTA, a rigid body equipped with six biaxial accelerometers. It is demonstrated that the new method significantly reduces the errors when computing the angular velocity of a rigid body from the accelerometer measurements.

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A cable inspection robot is proposed to automatically check the cables of a cable-stayed bridge. First, a climbing model supported by an independent spring and an inspection robot is designed. Second, the dimensionless parameter, h/r, which is the ratio of the vertical height of the obstacle to the radius of the obstacle-climbing wheel, is selected as the evaluation standard of the climbing ability of the robot; after which a mathematical model of such obstacle-climbing ability is established. Third, the bearing capacity of the driving wheel rubber is studied using the finite element method. Afterwards, the analysis of the climbing performance is then carried out through simulation by studying two influential perspectives, namely, the positive pressure from the passive end spring and the swinging angle of the passive wheel. Finally, field experiments are carried out on the HuangPu Cable-Stayed Bridge. Based on the results, the robot can climb steadily on various inclined cables.

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This work synthesizes the mechanism structures of the drawloom for pattern-weaving, which was illustrated unclearly in many ancient Chinese literatures. Based on the analysis of mechanism, the structural characteristics and design constraints of the mechanism with uncertain members and joints are concluded. Then, according to the concepts of generalization and specialization subject to the concluded design constraints, all feasible structures of mechanism that meet the technological standards of the subject’s time period are reconstructed including 16 and 8 design concepts for the heddle foot-falling device and the heddle foot-raising device, respectively. This reconstruction process provides a logical foundation to deal with the issue of the ancient mechanical drawings with uncertain members and joints.

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In this paper, a quaternion formulation of the power manipulability is developed. Quantifying the mechanical transmissibility of a mechanism, this parameter was previously introduced as a new homogeneous performance index of robot manipulators; however, its evaluation requires complex manipulations, particularly those of quadri-vectors. Furthermore, the quadri-vector form fits exactly with the structure of quaternions. Hence, a quaternion based method may be useful for power performance indices evaluation. It will be shown that this method leads to a recursive algorithm that manipulates kinematics’ parameters as matrices defined over the real quaternion space. Therefore, a new mostly simplified procedure is elaborated, which is suitable to robots performance analysis related issues. The resultant algorithm is largely simpler and more efficient to evaluate the power based performance indices.