Admittance Control of Four-link Bionic Knee Exoskeleton with Inertia Compensation

This paper proposes a control algorithm based on the admittance principle for the motion of the four-link bionic knee exoskeleton. Firstly, the interaction between the operator and the exoskeleton was converted into the desired trajectory of the exoskeleton. Then, the inertia compensation is achieved in light of the admittance features of exoskeleton movement. Finally, the validity of the admittance control method for four-link bionic knee was confirmed through simulation experiment. The simulation results show that the relative error of the joint angle between the operator and the exoskeleton was less than 5% at normal swinging frequency, and the interaction force between the manipulator and the exoskeleton was within ±0.5 N. The research findings lay a theoretical basis for practical application of exoskeletons

Design, Modeling and Control of Bionic Knee in Artificial Leg

The biped robot with heterogeneous legs (BRHL) greatly facilitates the development of intelligent lower-limb prosthesis (ILLP). In the BRHL, the remaining leg of the amputee is simulated by an artificial leg, which provides the bionic leg with the precise gait following trajectory. Therefore, the artificial leg must closely mimic the features of the human leg. After analyzing the motion mechanism of the human knee, this paper designs a four-link bionic knee in light of the coexistence of rolling and sliding between the femur, the meniscus and the tibia. Drawing on the driving mechanism of leg muscles, two pneumatic artificial muscles (PAMs) were adopted to serve as the extensor and flexor muscles on the thigh. The two PAMs move in opposite direction, driving the knee motions in the artificial leg. To overcome the complexity of traditional PAM modelling methods, the author set up a PAM feature test platform to disclose the features of the PAMs, and built static and dynamic nonlinear mathematical models of the PAMs based on the test data. Next, a proportional-integral-derivative (PID) closed loop controller and sliding mode controller was designed for the bionic knee, referring to the kinetics equation of the knee. Through experimental simulation, it is confirmed that the proposed controller can accurately control the position of the four-link bionic knee, and that the designed bionic knee and PAM driving mode are both correct

Coordinating a multi-retailer decentralized distribution system with random demand based on buyback and compensation contracts

Purpose: The purpose of this paper is to set up the coordinating mechanism for a decentralized distribution system consisting of a manufacturer and multiple independent retailers by means of contracts. It is in the two-stage supply chain system that all retailers sell an identical product made by the manufacturer and determine their order quantities which directly affect the expected profit of the supply chain with random demand. Design/methodology/approach: First comparison of the optimal order quantities in the centralized and decentralized system shows that the supply chain needs coordination. Then the coordination model is given based on buyback cost and compensation benefit. Finally the coordination mechanism is set up in which the manufacturer as the leader uses a buyback policy to incentive these retailers and the retailers pay profit returns to compensate the manufacturer. Findings: The results of a numerical example show that the perfect supply chain coordination and the flexible allocation of the profit can be achieved in the multi-retailer supply chain by the buyback and compensation contracts. Research limitations: The results based on assumptions might not completely hold in practice and the paper only focuses on studying a single product in two-stage supply chain Practical implications: The coordination mechanism is applicable to a realistic supply chain under a private information setting and the research results is the foundation of further developing the coordination mechanism for a realistic multi-stage supply chain system with more products. Originality/value: This paper focused on studying the coordination mechanism for a decentralized multi-retailer supply chain by the joint application of the buyback and compensation contracts. Furthermore the perfect supply chain coordination and the flexible allocation of the profit are achieved.Peer Reviewe

Coordinating a multi-retailer decentralized distribution system with random demand based on buyback and compensation contracts

Purpose: The purpose of this paper is to set up the coordinating mechanism for a decentralized distribution system consisting of a manufacturer and multiple independent retailers by means of contracts. It is in the two-stage supply chain system that all retailers sell an identical product made by the manufacturer and determine their order quantities which directly affect the expected profit of the supply chain with random demand. Design/methodology/approach: First comparison of the optimal order quantities in the centralized and decentralized system shows that the supply chain needs coordination. Then the coordination model is given based on buyback cost and compensation benefit. Finally the coordination mechanism is set up in which the manufacturer as the leader uses a buyback policy to incentive these retailers and the retailers pay profit returns to compensate the manufacturer. Findings: The results of a numerical example show that the perfect supply chain coordination and the flexible allocation of the profit can be achieved in the multi-retailer supply chain by the buyback and compensation contracts. Research limitations: The results based on assumptions might not completely hold in practice and the paper only focuses on studying a single product in two-stage supply chain Practical implications: The coordination mechanism is applicable to a realistic supply chain under a private information setting and the research results is the foundation of further developing the coordination mechanism for a realistic multi-stage supply chain system with more products. Originality/value: This paper focused on studying the coordination mechanism for a decentralized multi-retailer supply chain by the joint application of the buyback and compensation contracts. Furthermore the perfect supply chain coordination and the flexible allocation of the profit are achieved.Peer Reviewe

Research on module configuration design by case-based reasoning oriented on CNC machine tool

CNC alatni stroj je simbol razvijene proizvodne tehnologije. Uvođenje modularnog projekta u postupke projektiranja CNC alatnih strojeva ima važnu teoretsku i praktičnu vrijednost. Ovaj rad promiče metodu projektiranja konfiguracije modula kombiniranjem modularnog projektiranja i promišljanja zasnovanog na slučaju (case-based reasoning-CBR). Riješeni su ključni tehnološki postupci uključujući transformaciju zahtjeva kupca, pronalaženje sličnog slučaja i procjenu slučaja. U radu su analizirani primanje i transformacija zahtjeva kupaca i mapiranje prema procjenama važnosti zahtjeva kupaca do procjena važnosti tehničkih karakteristika proizvoda. Proučavane su tehnologije CBR-a i primijenjen je fuzzy omjer prioriteta sličnosti i algoritam Grey analize korelacije kako bi se odredio i procijenio slučaj koji ima prioritet te izabrao slučaj proizvoda koji konačno najbolje odgovara zahtjevima kupca. Izabrana je CNC horizontalna tokarilica kao primjer učinkovitosti algoritma.CNC machine tool is a symbol of advanced manufacturing technology. The introduction of modular design into the design processes of CNC machine tool has important theoretical and practical value. Combining modular design with case-based reasoning (CBR), this paper puts forward one method of module configuration design. The key technologies including the transformation of customer requirements, the case retrieval and the case evaluation have been solved. This paper analysed the acquisition and transformation of customer requirements, and the mappings from the importance ratings of customer requirements to the importance ratings of product technical characteristics. The paper studied the technologies of CBR, and used the fuzzy similarity priority ratio and grey correlation analysis algorithm to realize the calculation of case priority and the case evaluation, and picked out the product case that best matches the customer requirements finally. CNC horizontal lathe is selected as an example to show the algorithm effectiveness

Product Family Modeling Method for Rapid Response Design

Abstract. Design resources reuse is very important to the rapid response design. In this paper, a design resources reusable model based on product family is established to meet the rapid response design. Firstly, parameters transmission structure of product family is constructed based on Generic Bill of Materials (GBOM) and product master model, and then the reused design resource library is established by the instantiation to master model. Finally product configuration management and variant design is realized on the basis of the reused design resource library. In the developing process of the rapid response design system of machine tool component, the Linear Motion (LM) rolling guide variant design subsystem is developed by the application of the above methods to realize the variant design and configuration management of LM rolling guide. The result shows that the method can provide a reliable guarantee for establishment and effective management of corporate design resource base

Prediction of Limb Joint Angles Based on Multi-Source Signals by GS-GRNN for Exoskeleton Wearer

To enable exoskeleton wearers to walk on level ground, estimation of lower limb movement is particularly indispensable. In fact, it allows the exoskeleton to follow the human movement in real time. In this paper, the general regression neural network optimized by golden section algorithm (GS-GRNN) is used to realize prediction of the human lower limb joint angle. The human body hip joint angle and the surface electromyographic (sEMG) signals of the thigh muscles are taken as the inputs of a neural network to predict joint angles of lower limbs. To improve the prediction accuracy in different gait phases, the plantar pressure signals are also added into the input. After that, the error between the prediction result and the actual data decreases significantly. Finally, compared with the prediction result of the BP neural network, GRNN shows splendid prediction performance for its less processing time and higher prediction accuracy

Development and Physical Control Research on Prototype Artificial Leg

To provide an ideal platform for research on intelligent bionic leg (IBL), this paper proposes a model of a biped robot with heterogeneous legs (BRHL). A prototype of an artificial leg is developed based on biological structure and motion principle analysis of human lower extremities. With regard to the driving sources, servomotors are chosen for the hip joint and ankle joint, while pneumatic muscle actuators (PMAs) are chosen for the knee joint. The control system of the bionic artificial leg is designed and a physical experimental platform is established. The physical control experiments are done based on proportional-integral-derivative (PID) control strategy. The experimental results show that such a system can realize the expected goals

Bionics Design of Artificial Leg and Experimental Modeling Research of Pneumatic Artificial Muscles

In the research and development of intelligent prosthesis, some of performance test experiments are required. In order to provide an ideal experimental platform for the performance test of intelligent prosthesis, a heterogeneous biped walking robot model is proposed. Artificial leg is an important part of heterogeneous biped walking robot, and its main function is to simulate the disabled a healthy normal gait, which provides intelligent bionic legs gait to follow the target trajectory. The pneumatic artificial muscles (PAM) have good application in the artificial leg. The bionic design of artificial leg mainly includes the structure of hip joint, knee joint, and ankle joint, adopting the four-bar mechanism as the mechanical structure of the knee joint, and PAM are used as the driving source of the knee joint. Secondly, the PAM performance test platform is built to establish the relationship among output force, shrinkage rate, and input pressure under the measured isobaric conditions, and the mathematical model of PAM is established. Finally, the virtual prototype technology is used to build a joint simulation platform, and PID control algorithm is used for verification simulation. The results show that the artificial leg can follow the target trajectory

Research on PDA-based Predictive Maintenance System of CNC Machine Tools

Abstract: The research on the predictive maintenance system of CNC machine tools based on PDA is of great theoretical significance and practical application value. This paper studied PDA-based predictive maintenance system of CNC machine tools using predictive maintenance theory as a guide to obtain the work state of CNC machine tools in machining process. The corresponding acoustic emission sensors, acceleration sensors and speed sensors are installed on CNC machine tools, by which PDA collected the information of tool machining process. If collected data is found abnormal, the warning module sends the alarm information to the staff via email or SMS and monitors the work state of CNC machine tools. Based on HP iPAQ hx2490 with data acquisition card, the sensor and other hardware equipment, the structure of hardware platform is completed. Employing LabVIEW, the system modules including data acquisition, email warning, SMS warning, login, and report generation are developed. This paper carried out positive exploration on the design of PDA-based portable data acquisition platform, data communication, the early warning maintenance