Theoretical Analysis and Experiment on Flow Allocation Characteristics of Dual Discharging Axial Piston Pump

通过改变缸体结构、柱塞数、端盖油路、配流盘形状等,设计了双排油内外环并联配流结构的轴向柱塞泵,实现了单柱塞泵两路高压供油。针对单环柱塞数减少,腔; 内压力冲击增大,脉动变大等问题,对配流结构进行重新设计。在排油腰形槽和吸油腰形槽过渡区取消卸荷槽,利用加大配错角,在排油完毕未接通吸油时,腔内封; 闭体积增大,未排尽的高压油液压力降低;在吸油腰形槽和排油腰形槽过渡区,排油卸荷槽利用阶梯变化通流面积代替原连续变化的通流面积,削弱了卸荷槽几何形; 状要求。重新设计后的双排油配流结构,以45mL轴向柱塞泵结构为参考,对配流结构进行了理论分析,建立了双排油轴向柱塞泵仿真模型。以单柱塞腔内压力; 冲击、输出流量进行分析研究,得外环压力冲击小,与传统配流结构相比较双排油输出口压力脉动变化率变小,并试制双排油轴向柱塞泵。对试制泵进行压力脉动测; 试、容积效率测试和噪声测试,结果表明,与45mL轴向柱塞泵进行对比,压力脉动降低了约30%,噪声也降低,容积效率不低于0.92。该双排油轴向柱; 塞泵可以代替双联泵,使系统结构简化,能耗降低。When providing two-way independent high-pressure high-flow oil sources,; hydraulic system generally adopts two separate piston pumps or coaxial; ones in series, causing complex structure and high cost. Therefore,; single piston pump was proposed to achieve two-way high-pressure oil; supply. Axial piston pump was designed with dual discharging inter-outer; ring parallel allocation structure by changing cylinder structure,; piston number, cap circuit and valve plate shape. Flow allocation; structure was redesigned due to decreased single ring piston number,; increased pressure shock and fluctuation in the chamber. Relief notch; was cancelled in transition region from oil-discharging to oil-absorbing; waist slots. After that, mismatch angle was increased to enlarge closed; volume in chamber and reduce the pressure of unexhausted high-pressure; oil in the interval between oil extraction and absorption. In transition; region from oil-absorbing to oil-discharging waist slots, stepped flow; area was used to replace original continuous flow area to weaken; geometry requirements of relief notch. The optimized dual discharging; flow allocation structure was conducted with theoretical analysis to; establish dual discharging axial piston pump simulation model based on; 45mL axial piston pump structure. There was small pressure shock in; outer race by analyzing pressure shock and output flow in single piston; chamber. Compared with traditional flow allocation structure, dual; discharging oil output had smaller pressure fluctuation rate. Based on; this, the designed dual discharging axial piston pump was piloted. The; pilot dual discharging oil pump was compared with the original 45mL; pump through pressure fluctuation, volumetric efficiency and noise; tests. Result showed that the former had lower pressure fluctuation; (decreased by 30%) and noise level, while its volumetric efficiency was; not smaller than 92%. In general, the dual discharging axial piston pump; can replace duplex pump to simplify system structure and reduce energy; consumption. This new pump can also be used in closed circuit and; differential cylinder hydraulic systems to make the system simpler and; cost-effective.山西省自然科学基金项目; 国家自然科学基金项

The Soft-SixthFinger: a wearable EMG controlled robotic extra-finger for grasp compensation in chronic stroke patients

This letter presents the Soft-SixthFinger, a wearable robotic extra-finger designed to be used by chronic stroke patients to compensate for the missing hand function of their paretic limb. The extra-finger is an underactuated modular structure worn on the paretic forearm by means of an elastic band. The device and the paretic hand/arm act like the two parts of a gripper working together to hold an object. The patient can control the flexion/extension of the robotic finger through the eCap, an electromyography-based (EMG) interface embedded in a cap. The user can control the device by contracting the frontalis muscle. Such contraction can be achieved simply moving his or her eyebrows upwards. The Soft-SixthFinger has been designed as tool that can be used by chronic stroke patients to compensate for grasping in many activities of daily living (ADL). It can be wrapped around the wrist and worn as a bracelet when not used. The light weight and the complete wireless connection with the EMG interface guarantee a high portability and wearability. We tested the device with qualitative experiments involving six chronic stroke patients. Results show that the proposed system significantly improves the performances of the patients in the proposed tests and, more in general, their autonomy in ADL

Study on wearable system for daily life support using McKibben pneumatic artificial muscle

This paper proposes the basic technologies in order to develop a wearable hand assistive system for daily life support. Current prosthetics have some problems for wearability. We focus on the load caused by weight of wearable system. The actuator is one of the heaviest parts in wearable systems. Therefore we propose to use the McKibben pneumatic artificial muscle which is lightweight and compact in size. At first, we propose a new method to control air pressure of artificial muscle without pressure sensor in order to reduce the size of system. Second, we investigate variable stiffness of human finger to perform human finger dexterity and simulate it by using our proposed polyarticular tendon drive system. ©2010 IEEE

Bio-inspired Mechatronic Design for the Actuation of a Soft Orthosis for Rehabilitation and Assistance of Hands

Proyecto de Graduación (Licenciatura en Ingeniería en Mecatrónica) Instituto Tecnológico de Costa Rica. Escuela de Ingeniería en Mecatrónica, 2010.It is described the design of a mechatronic system to actuate a hand soft orthotic device for rehabilitation and assistance purposes developed by the author of this thesis within the Bio Mechatronics Department of Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) based in Stuttgart, Germany. The system mimics the musculoskeletal anatomy and kinesiology of the human body by resembling the bone-muscle-tendon configuration. A key feature of the orthosis is that allows the individual movement of the fingers. The actuation consists in the use of -high contraction- Festo Pneumatic Artificial Muscles (PAMs) within a 3D printed support structure which was designed using anthropometric data to aim to comfort and ergonomics. The PAMs are operated with piezoelectric -flow proportional- valves. The sensors mimic the human somatosensory system to control the motion and to confer a haptic nature to the human interface. The use of light indicators allows visual reinforcement during exercises. The final deliverable is a testing model that is going to be used for further experiments. Finally, this orthotic device is envisioned to become a mobile solution for self-aided rehabilitation.Instituto Tecnológico de Costa Rica. Escuela de Ingeniería en Mecatrónica. Fraunhofer Institute for Manufacturing Engineering and Automation (Fraunhofer IPA)