Chen-Chou Lin

The force transmissivity index of planar linkage mechanisms

In this paper, a new force transmissivity index (FTI) of planar linkage mechanisms is proposed. The index is used to quantitatively measure the force transmission quality from the input link to an output link. Traditionally, the transmission angle is used to measure the ability to transmit motion for planar four-bar linkages. However, the transmission angle is usually limited to be used at four-bar linkages due to the structural simplicity. For complex multi-loop mechanisms, it is often difficult to define the force transmissivity. Here we have established a procedure of force transmissivity analysis for planar linkage mechanisms. The method is based on the static force analysis and the concept of power flow path. It is found that the force transmissivity of a mechanism depends not only on the configurations of the mechanism, but also on the selection of the output link and the forms of the loading. We have compared the results based on the FTI with the results from the Jacobian matrix method and the joint force index (JFI) method for four-bar mechanisms. It shows that the proposed FTI can describe the force transmission performance more accurately than other methods do. It is concluded that the index can be used as a better measure of force transmissivity analysis for planar linkage mechanisms.

Force Transmissibility Performance of Parallel Manipulators

In this paper, a new force transmission index called the mean force transmission index (MFTI) is proposed, and the force transmissibility analysis procedure is established for parallel manipulators. The MFTI is an extended definition of the force transmission index (FTI) introduced by the authors previously. It is shown that the FTI is a function of the input velocity ratio (IVR) for a multi-DOF mechanism of the same configuration. To represent the force transmissibility by a definite value, the MFTI is defined as the mean value of the normalized FTIs function over the whole range of the IVR. The force transmissibility analysis of two planar parallel manipulators is illustrated using the MFTI method. The result is compared with that of the Jacobian matrix method and the joint force index (JFI) method. It shows that, especially for symmetric parallel manipulators, an approximate inverse-proportionality relationship exists between the JFI and MFTI, and between the maximum input torque/force and MFTI. It is concluded that the MFTI can be used as a quantitative measure of the force transmissibility performance for parallel manipulators. In the end, a design optimization problem is studied by taking the

Inspecting Profile Errors of Conjugate Disk Cams With Coordinate Measurement

To inspect cam profile errors, a coordinate measuring machine (CMM) is frequently employed. The coordinate data of discrete points at the cam surface are measured by a CMM in order to further evaluate the actual cam profile with complicated interpolation algorithms, and then the cam contour approximated by these algorithms may be compared with the theoretical one. In this paper, a direct and simple analytical method, instead of a numerical interpolation algorithm, is proposed for inspecting the profile deviations of conjugate disk cams with coordinate measurement data. The method is based on the derived correlation between the radial-dimension errors and the normal-direction errors of conjugate cam profiles. To verify the proposed method, an experiment of inspecting a pair of conjugate disk cam profiles was conducted. The experimental results obtained from the proposed method were compared with those obtained by using the Hermite interpolation method. It shows that this method is accurate and more efficient for inspecting the profile errors of conjugate disk cams.

The study of remotely teleoperated robotic manipulator system for underwater construction

Most commercial underwater manipulators to date belong to master-slave type. The disadvantage of the system is that it requires the operator be well trained and fully skilled. Hence a robot manipulator system with high intelligence should be developed to fulfill the need of less-skilled or even non-skilled operators. In response to the above needs, we have designed and implemented an intelligent underwater robotic manipulator system to enhance the capability of the robotic manipulator. This developing system consists of a manipulator, a distance measurement system, water-proof camera, computer, interface technology and task planning technology etc. The system is constructed as a windows-guided, supervisory underwater robotic manipulator system. The underwater manipulator was designed and fabricated to be an articulate type robot with five rotary joints, including waist, shoulder, elbow, wrist-pitch, and wrist-roll motion. The system consists four subsystems to facilitate the intelligence behavior of the robotic system. The modules include a task planning module, an image process and identification module a distance measurement module, and a motion planning and control module. A prototype of teleoperated underwater robotic manipulator systems has been setup. The finished prototype underwater manipulator system have been used as a test station for underwater operation, to crip and more a object. The set up system is hanged under a manipulator is installed on the 6 degrees of freedom rotation platforms to simulate ROV motion under sea. The remotely teleoperated robot manipulator system hanged under the 6 degrees of freedom rotation platform can finish a underwater construction. To demonstrate the ability of the underwater robotic manipulator system, we designed an experiment for the underwater manipulator under the 6 degrees of freedom rotation platforms to simulating ROV under sea to accomplish an object crip under water with robotic system. The task planning module incorporated with the commands from the control panel, forms the highest control level of the system. In the manipulator system, the image module functions as a pre-process. It deals with tasks such as extracting target objects from CCD-images, and more importantly, providing information needed by the planning module. In distance measurement module, we have test ultrasonic and laser distance measurement system to offer main system accuracy distance information. In the motion planning and control module, the coordinates of the target position are obtained from the task planning module, then the inverse kinematics of the manipulator is performed to derive the joint angle for each joint.

The trajectory analysis of bevel planetary gear trains

In this paper, the trajectory of bevel planetary gear trains has been studied. The parametric equations of trajectory are derived. It is shown that the trajectory generated by a tracer point on the planet of a bevel planetary gear train is analogous to that of a spur planetary gear train. Two cases, gear ratio equal to one and two, are presented in detail including the geometric description, plane of symmetry, extent of trajectory, number of nodes (cusps) and their locations. The criteria for the existence of cusps are verified algebraically, and interpreted from geometrical point of view.

Theoretical Analysis and Sph Simulation for the Wave Energy Captured by a Bottom-Hinged OWSC

This paper examines one type of wave energy converter, the Oscillating Wave Surge Converter (OWSC) with its bottom hinged on the sea bed. The simplest form of OWSC is a flapper connected with a power take-off (PTO). Theoretical analysis based on a 2D linear potential theory elucidates the mechanisms of the wave energy capture by a bottom-hinged OWSC in terms of impedances associated with the wave field, the flapper body, and the PTO. Criteria of impedance canceling and matching to maximize the energy capture factor can be deduced. Smoothed Particle Hydrodynamics (SPH) is established for simulating the same problem, and the trends of SPH results match that of the theoretical prediction well. Therefore, SPH can be regarded as a reliable numerical tool for designing and optimizing OWSCs.

NUMERICAL MODELING OF WAVE-INDUCED ROTATIONS OF A BOTTOM-HINGED FLAPPER WITH A SPH MODEL

In this study, a Smoothed Particle Hydrodynamics model for simulating wave-induced rotations of a bottom-hinged flapper was established in a 2-D numerical wave flume. The simulated rotating angles illustrated that the flapper could swing back and forth following harmonic wave loadings. The simulations were also seen to be in good agreement with experimental data, confirming the applicability of the present numerical model. The simulated hydrodynamic behaviors at different phases showed that the flapper moved downstream under the wave crest and upstream under the wave trough following the elliptical form of water particle trajectory. The energy conversions of a flapper during an average wave cycle showed that larger rotating angle ranges could result in higher energy conversions. However, smaller rotating angle ranges could result in higher captured efficiency.

Numerical Assessment on Wave Energy Resources in Coastal Waters of Northeastern Taiwan

To assess wave power resources at a marine energy test site in Keelung coastal waters, the SWAN (Simulating WAve Nearshore) model [1; 2] is applied to obtain wave conditions for assessing the wave energy resources. The ocean surface wind velocity by CCMP (Cross-Calibrated Mutli-Platform) is first adopted in SWAN model simulation. Comparisons with field measurements of AWCP (Acoustic Water Column Profiler) station in Port of Keelung and of ADCP (Acoustic Doppler Current Profiler) station offshore NTOU (National Taiwan Ocean University) during periods form Jul 1st to Dec 31st of 2010, show that simulated significant wave heights agree well with measured values except in periods of typhoons and strong northeastern monsoons. However, the simulated peak periods are generally underestimated than the measurements. The same results can also be seen in simulated wave energies. The resulting simulated wave energies agree with measurements better at NTOU test site than at Keelung station.Copyright

A knee arthrometer for measuring varus, valgus, and rotation

Due to the characteristics of cruciate ligaments, knee ligament tears are not suitable to heal by remedy. Anterior cruciate ligament (ACL) reconstruction is one of the most common and reliable surgeries to handle knee ligament injuries. To date, most knee ligament reconstructions can be done by using endoscopic surgery. Although single bundle ACL reconstructions could improve the recovery of knee function, yet it was still not enough for the stability of the knee joint. In some cases instability might even develop to be osteoarthritis. Via some vitro tests, such as varus, valgus and rotation tests, the test results showed that the ligament after single bundle ACL reconstruction was not able to bear the rotational, and varus/valgus torque at the knee joint. That means using conventional arthrometer such as KT-1000 could lead to misdiagnosis in the above mentioned situation. We developed a new instrument to measure the extent of tibias varus, valgus and rotation relative to the femur. Via the test data, the instrument could quantify the knee laxity and help surgeon to diagnose the injured knee more accurately and verify whether an ACL reconstruction was successful. The main function of the instrument is to test knee ligament laxity by measuring the varus/valgus angulation, and internal/external rotation with high sensitivity and data reproducibility. We verified the instruments performance via experiments. The results of the experiments demonstrated the usability of the arthrometer.

The design and preliminary assessment of a new knee ligament arthrometer

The paper introduces a new knee ligament arthrometer with dual functions. The arthrometer provides not only the traditional function to test the laxity anterior/posterior cruciate ligaments, but also the function to test the laxity of the medial/lateral collateral ligaments. The preliminary assessment about the data reproducibility was conducted. It showed that the new arthrometer performed well in the aspect of data reproducibility. Further assessment of the arthrometer will be conducted, and the reliability need to be established by comparing with the existing arthrometer.