Research On The Kev Technologies Of The Hydraulic Lower Limb Exoskeleton Robot

A Lower-limb Exoskeleton for Power Assist(LEPA)is an intelligent robot that is used to assist the movement of the wearer by improving the walk duration,speed and carrying capacity.The LEPA can achieve a variety of movement such as walking,running,or jumping,and plays an important role in many fields such as battle field,escue scenes,or construction sites where road transports are absent.Therefore the research of the LEPA is an international academic frontier,the technological challenge lies in the realization of high load capacity,high power density,and long working time.This thesis is aimed at the key technologies of the LEPA.The innovations in this thesis are summerized as follows.1.A power system of the exoskeleton robot with high power density is developed.Lithium batteries are used by most of the exoskeletal robots as energy supply,however the energy density of the lithium battery is small,and it is difficult to ensure high power or long working hours.To solve this problem,an engine-driven power system was developed,which weights approximately 20kg and provides 1.5kW hydraulic power as well as 160W electrical power.The power system can work 4.5 hours continuously at 1.2kW rated power with 5kg fuel.As a contrast,the weight of the power system(with fuel)is about 64%of the battery based power unit that meets the same power and capacity.2.A graphical multi-objective optimization method is proposed.A spring-pressurized reservoir is developed for implementing closed hydraulic circuit,which prevents air sucktion,contamination or pump cavitation.There are six optimization objectives of the reservoir,such as weight,special volume and pressurization.The existing multi-objective optimization(MOO)methods rely on the preference model to balance objectives.However it's difficult to model preference information because of many optimization objectives and the objectives on different aspects cannot be compared.The proposed MOO method displays optimization results graphically,and advances in the clear decision flow and the intuitive display of optimal solutions,makes up for the existing methods which output data as results.The proposed method can help designers to get the final solution quickly and easily,without the need to provide the performance model of the optimization problem,thus can be more widely used in practical problems.3.A highly integrated controller is developed,and a multi-task dynamic scheduling framework for controller is proposed.The controller is designed in a motherboard/functional module structure,and has advantages in low operating voltage,low power consumption,and easy to expand and improve.In the operation of the controller,a large number of tasks are required to be scheduled and executed.In response to this requirement a multi-task scheduling architecture is proposed,where an active task list is maintained by taking advantages of the inter-task dependency.Tasks can be scheduled concurrently according to the active task list without the adoption of RTOS,and the time loss on the synchronization mechanism and RTOS task scheduling,as well as the loss of storage space can be avoided.The thesis is organized as follows:In chapter 1,the development status of the lower-limb exoskeleton for power assist is summarized;the characteristics and demands of the application environment of the exoskeletal robot are analyzed.The main research contents of this subject are clarified,where the engine-driven hydraulic actuatation is adopted.The difficulty of this research is pointed out.In chapter 2 the development and characteristics of the lower limb mechanism are discussed.The structural strength,carrying capacity,and the wearer protection measures are taken into consideration.The gait data is acquired to backup the development by a customized device.The active joints driven by servo-valve controlled asymmetric cylinders are discussed in detail,which guarantees sufficient drive force.The kinematic and static model of the lower limb mechanism is also analysed.In chapter 3 the development and characteristics of the power system are discussed.The advantages of the engine-fuel scheme are demonstrated by comparison to the battery scheme.The prime mover module,the hydraulic circuit and the generator module are analysed in detail,and the power system prototype is developed.An innovative graphic multi-objective optimization method is proposed and used to optimize a spring pressurized reservoir,which completes the closed hydraulic circuit.The engine power model and load flowrate estimation model is analysed.In chapter 4 the development and characteristics of the hardware and program of the control system is discussed.The control system consists of a mother-board and several functional extended modules.The implementation of data acquisition(DAQ)modules and drive modules are discussed,and the precision of DAQ is analysed.The stratification and operation of the control system software is elaborated,and a multi-task scheduling architecture is proposed.In chapter 5 the experimental research on the exoskeleton robot prototype is demonstrated and analyzed,where the performance of the power unit and the movement characteristics of the limb are presented.The experimental study is carried out in the aspects of the power system,the no-load limb motion as well as the experimental walking behavior of the prototype.The models in previous chapters are also validated.In chapter 6 the previous chapters are summarized.The research achievements and innovation is highlighted.Suggestions are also provided for the future work.