Chung-Huang Yu

Using an Optimization Approach to Design an Insole for Lowering Plantar Fascia Stress—A Finite Element Study

Plantar heel pain is a commonly encountered orthopedic problem and is most often caused by plantar fasciitis. In recent years, different shapes of insole have been used to treat plantar fasciitis. However, little research has been focused on the junction stress between the plantar fascia and the calcaneus when wearing different shapes of insole. Therefore, this study aimed to employ a finite element (FE) method to investigate the relationship between different shapes of insole and the junction stress, and accordingly design an optimal insole to lower fascia stress.A detailed 3D foot FE model was created using ANSYS 9.0 software. The FE model calculation was compared to the Pedar device measurements to validate the FE model. After the FE model validation, this study conducted parametric analysis of six different insoles and used optimization analysis to determine the optimal insole which minimized the junction stress between plantar fascia and calcaneus.This FE analysis found that the plantar fascia stress and peak pressure when using the optimal insole were lower by 14% and 38.9%, respectively, than those when using the flat insole. In addition, the stress variation in plantar fascia was associated with the different shapes of insole.

A strategy used by paraplegics to stand up using FES

Many paraplegics can stand up if their leg extensor muscles are stimulated without feedback to the stimulator-controller. Their neurologically-intact upper bodies control the motion by exerting forces through the arms. To develop stimulator-controllers, we wish to understand the strategy they use. In two subjects, we measured the handle forces and the posture during standing up. Plotted so as to relate the handle forces to the leg joints, the results show that the upper body helps extend the knees and then the hips: a strategy we call quick knee-locking. This may keep the upper body forces within the limits of its strength.

The effect of design variables of condylar total knees on the joint forces in step climbing based on a computer model.

The ability to climb a steep step or rise from a low chair after total knee replacement may be enhanced if the required force in the quadriceps muscle is reduced. This can potentially be achieved if the total knee produces a large lever arm measured from the femoral-tibial contact point to the patellar ligament. A reduced quadriceps force would also reduce the patello-femoral force and the femoral-tibial contact force. The contact point location is likely to be a function of the geometry of the femoral and tibial components in the sagittal plane, including the relative distal and posterior radii of the femoral profile, the location of the bottom-of-the-dish of the tibial surface, the radius of the tibial surface, and the presence or absence of the posterior cruciate ligament. A three-dimensional model of the knee was developed including the quadriceps and various ligaments. In the study, the motion was confined to flexion extension and displacement in the sagittal plane. The quadriceps was assumed to be the only muscle acting. A standard software package (Pro/Mechanica) was used for the analysis. For a femoral component with a smaller distal radius, there was 12% reduction in the quadriceps muscle force and up to 11% reduction in the patello-femoral force from about 100 up to 60 degrees flexion. However, apart from that, there were less than 10% differences in all the forces as a function of all of the design variables studied. This was attributed to the relatively small changes in the lever arm of the patella tendon, since the tendon moves in an anterior-posterior direction along with the femur. An additional factor explaining the results was the change in the anterior-posterior contact point as controlled by the forces in the patella tendon and in the soft tissues. The results imply that for a standard condylar replacement knee, the muscle and contact forces are not greatly affected by the geometrical design variables.

Identification and classification of multi-degree-of-freedom and multi-loop mechanisms

This study concerns the degree-of-freedom, the arrangements of input and the type of mobility of multi-loop, multi-degree-of-freedom mechanisms. Firstly, «basic loops» are introduced, and a systematic scheme for identifying the actual degree-of-freedom of mechanisms is developed. The input, then, can be properly deployed, such that the mechanism has a totally constrained motion. Lastly, based on the input deployment, the mobility of mechanisms is classifed and identified into three types: total, partial and fractionated mobility. The procedure has been automated, and the atlas of all possible arrangements of input of up to eight-linkplanar mechanisms with only revolute joints is presented. The systematic method is helpful for the structural synthesis of multi-degree-of-freedom and multi-loop mechanisms, and for exploring their potential industrial applications

The Performance Improvements of Train Suspension Systems with Inerters

This paper investigates the performance benefits of train suspension systems employing a new mechanical network element, called inerter. Combined with traditional passive suspension elements - dampers and springs, inerter is shown to be capable of improving the performance, in terms of the passenger comfort, system dynamics and stability (safety), of the train suspension systems. Furthermore, a motor-driven platform is constructed to test the properties of suspension struts with inerters

Optimization of the Sit-to-Stand Motion

This paper proposes a method to evaluate the influence of moving tracks on body loadings. The sit-to-stand movement is selected and analyzed, in order to illustrate how a special form of physical therapy known as the Alexander technique can effectively reduce the loads placed on the joints. Because force and moment sensors cannot be implemented to take direct measurements within the joints, we used a motion analysis system to analyze information about body position and then input the data into ADAMS models to estimate the reaction forces and moments on the joints. Furthermore, an optimal control algorithm is introduced to quantitatively identify the optimal contours of the movements. By analyzing the reactions of the joints, this paper demonstrates that better moving tracks are beneficial for reducing body loads.

Robust Control of a Two-Axis Piezoelectric Nano-Positioning Stage

Abstract This paper applies robust control to a two-axis piezoelectric nano-positioning stage. As technology develops, the precision requirement for positioning platforms is becoming increasingly stringent. Since a traditional mechanical transmission structure cannot achieve high precision, a piezoelectric actuator is usually applied to drive the mechanism because of its high resolution, high accuracy, and large driving force. However, the non-linear dynamic characteristics of piezoelectric materials, such as hysteresis, might degrade system performance. Therefore, in the present study, we model a piezoelectric stage as a linear system, and regard the nonlinear factors as system uncertainties. We then apply robust control strategies to guarantee system stability and performance. Lastly, the designed controllers are implemented for experimental verification. The results demonstrate the effectiveness of these robust controllers.

Measurement of posture by triangulation using potentiometers

To measure the posture of a paraplegic while standing up, an economical method has been developed. Markers, glued over the joints, hook onto strings which run to rotary potentiometers mounted on a fixed frame. Springs maintain a near-constant small tension in the strings, and the potentiometers rotate as the strings wind onto pulleys. The positions are calculated by triangulation, using two potentiometers per joint, assuming that body segment lengths are constant, or three potentiometers without this assumption. Using a second-order polynomial fit, the random error in length measurement for each potentiometer is less than +/-2 mm for the string length from 0 mm to 1100 mm, or less than +/-1 mm in actual range from 600 mm to 1000 mm. With two potentiometers per joint, using a second-order polynomial fit and assuming the ankle position is known exactly, an estimate of the resulting errors in the knee and hip marker positions are 4 and 8.5 mm, respectively.

Design and implementation of robust controllers for a gait trainer

Abstract This paper applies robust algorithms to control an active gait trainer for children with walking disabilities. Compared with traditional rehabilitation procedures, in which two or three trainers are required to assist the patient, a motor-driven mechanism was constructed to improve the efficiency of the procedures. First, a six-bar mechanism was designed and constructed to mimic the trajectory of childrens ankles in walking. Second, system identification techniques were applied to obtain system transfer functions at different operating points by experiments. Third, robust control algorithms were used to design H∞ robust controllers for the system. Finally, the designed controllers were implemented to verify experimentally the system performance. From the results, the proposed robust control strategies are shown to be effective.

An interactive wireless communication system for visually impaired people using city bus transport

Visually impaired people have difficulty accessing information about public transportation systems. Several systems have been developed for assisting visually impaired and blind people to use the city bus. Most systems provide only one-way communication and require high-cost and complex equipment. The purpose of this study is to reduce the difficulties faced by visually impaired people when taking city buses, using an interactive wireless communication system. The system comprised a user module and a bus module to establish a direct one-to-one connection. When the user inputs 4-digit numbers, the user module immediately sends out the information. If the bus module receives the matched bus number, it buzzes and the warning LED flashes to notify the bus driver that someone is waiting to board on the bus. User tests were conducted by two visually impaired people in a simulated vehicle and a city bus. The success rate of interactive wireless communication, recognizing the arrival of the bus and boarding the correct bus reached 100% in all of the tests. The interactive wireless communication aid system is a valid and low-cost device for assisting visually impaired people to use city buses.