A Novel Design Concept of Digital Hydraulic Drive for Knee Exoskeleton

2021 ◽  
Author(s):  
Rituraj Rituraj ◽  
Rudolf Scheidl ◽  
Peter Ladner ◽  
Martin Lauber
Keyword(s):  
Gait Cycle ◽  
Hydraulic Drive ◽  
Cost Effective ◽  
Peak Torque ◽  
Energy Recuperation ◽  
Moderate Power ◽  
Hydraulic Cylinders ◽  
Exoskeleton Design ◽  
Novel Design ◽  
Unique Mechanism

Abstract Hydraulic actuation of exoskeletons has gained interest among researchers due the potentials of high power density and energy recuperation allowing the reduction of mass and space used by the device (when compared to the traditional electrically actuated exoskeletons). However, developing a light and cost-effective design of such exoskeleton remains a key challenge. In this work, a novel design of digitally driven knee exoskeleton is presented. The design uses simple hydraulic cylinders instead of multi-chamber cylinders (which are typically used in digital actuations and are expensive). The design also includes a unique mechanism that is able to satisfy the peak torque requirements during a typical gait cycle with a smaller hydraulic force. This ensures small size of hydraulic components and a moderate power demand from the energy source. To study this exoskeleton design, a numerical model of the exoskeleton and the lower limb is developed in this work. The simulation results show that the design is able to track the motion of the knee in a typical gait cycle as well as satisfy the necessary torque requirements.

scholarly journals Electro-Hydraulic Drive of the Variable Ratio Lifting Device under Active Load

2021 ◽  
pp. 599-610
Author(s):  
Andrzej Kosucki ◽  
Łukasz Stawiński ◽  
Adrian Morawiec ◽  
Jarosław Goszczak
Keyword(s):  
Asynchronous Motor ◽  
Experimental Studies ◽  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Open Loop ◽  
Control Mode ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Energy Recuperation ◽  
Hydraulic Cylinders

Hydraulic systems fed by fixed displacement pumps driven by frequency-controlled electric motors can replace conventional throttling systems due to their ability to control the speed of hydraulic cylinders regardless of the value and direction of the load. These systems can improve the energy efficiency of the drive or even provide the possibility of energy recuperation during lowering. This paper presents experimental studies of the new drive system with volumetric control of the speed of the lifted/lowered payload using the example of a scissor lift. The system uses a reversible gear pump driven by an asynchronous motor fed by a frequency inverter operating in field-oriented control mode. Comparative studies of the mapping of the assumed speed of the hydraulic cylinder and platform are presented, as well as studies of the influence of the load change on the speed and positioning of the mechanism driven by the open-loop controlled system.

Development of hydraulic cylinder diagnostic methods by modeling methods

2021 ◽  
pp. 41-45
Author(s):  
Keyword(s):  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Technical Condition ◽  
Diagnostic Methods ◽  
Technical Diagnostics ◽  
Remaining Service Life ◽  
Construction Machine ◽  
Piston Speed ◽  
Variable Nature ◽  
Hydraulic Cylinders

The hydraulic drive of a construction machine is a complex dynamic system that is subjected to many dynamic loads of a variable nature and operates under conditions of variable external influences caused by various factors. During operation, these loads cause failure of the hydraulic transmission elements. To prevent these malfunctions, technical diagnostics should be applied by determining their current technical condition and remaining service life. The article assesses the working condition of hydraulic cylinders using a mathematical model. Using matlab/simulink software to simulate the hydraulic cylinder and hydraulic piston speed when changing the hydraulic cylinder clearance. The simulation results are presented. Keywords: diagnostic, hydraulic cylinder, simulation, development

scholarly journals Theoretical background of hydraulic drive control system analysis for testing piston hydraulic cylinders

2019 ◽  
Vol 19 (3) ◽  
pp. 242-249 ◽  
Author(s):  
A. T. Rybak ◽  
I. K. Tsybriy ◽  
S. V. Nosachev ◽  
A. R. Zenin
Keyword(s):  
Mathematical Modeling ◽  
Hydraulic System ◽  
Energy Recovery ◽  
Test Bench ◽  
Hydraulic Drive ◽  
Mechanical Transmission ◽  
Hydraulic Motor ◽  
Hydraulic Machines ◽  
Life Tests ◽  
Hydraulic Cylinders

Introduction. The durability and performance of hydraulic machines is determined through life tests. At that, various braking devices (mechanical, electric, hydraulic, etc.) are used for strength loading of the hydraulic motor, as a result of which a significant amount of energy is lost. This can be avoided if the method of rotational motion with energy recovery is used during life tests. This approach is applicable for hydraulic pumps, motors, and hydraulic cylinders.Materials and Methods. A test bench is presented, the design of which provides recreation of the conditions most appropriate for the field operation of hydraulic cylinders. In this case, energy recovery is possible. To solve the research problems, methods of mathematical modeling were used, the basic functional parameters of the proposed design were calculated. The determination of the pressure increment at various points in the hydraulic system is based on the theory of volumetric rigidity. When modeling the motion of the moving elements of the bench hydraulic system, the laws of rotor motion are used.Research Results. In the structure of the test bench, the cylinders in question are located in the pressure main between the hydraulic pump and the hydraulic motor. This enables to significantly reduce the bench itself and to save a significant amount of energy due to its recovery. A basic hydraulic diagram of the test bench for piston hydraulic cylinders is presented, in which the operation of the moving elements of the system is shown. A mathematical modeling of the hydraulic system of the bench is performed. A kinematic diagram of the mechanism for transmitting motion between test cylinders is shown.Discussion and Conclusions. The system of equations presented in the paper shows how the increment of pressure at the selected nodal points of the energy recovery system is determined (in particular, how the increment depends on time, reduced coefficient of volumetric rigidity, operating fluid consumption, and piston areas). The velocities of the hydraulic pistons are determined according to the kinematic scheme of the mechanical transmission of the bench. Thus it can be argued that, thanks to the solution presented in the paper, the life test results of hydraulic cylinders will adequately reflect their operation under rated duties.

Estimation of Torque Variation of Geohod Transmission with Hydraulic Drive

2013 ◽  
Vol 379 ◽  
pp. 11-15 ◽  
Author(s):  
Vladimir V. Aksenov ◽  
Mikhail Yu. Blaschuk ◽  
Mikhail V. Dubrovskii
Keyword(s):  
Hydraulic Drive ◽  
Transmission Parameters ◽  
Hydraulic Cylinders

The features of initiation of irregularity of rotation in geohod transmission with hydraulic cylinders in different phases are discussed in the present study. The procedure for determination of torque variation, as well as the effect of transmission parameters on the value of variation is described

scholarly journals Analysis of the Throttle Speed Control Efficiency in Volumetric Hydraulic Drives

2019 ◽  
pp. 13-33
Author(s):  
K. D. Efremova ◽  
V. N. Pilgunov
Keyword(s):  
Control Method ◽  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Movement Speed ◽  
Working Fluid ◽  
Total Efficiency ◽  
Control Methods ◽  
Output Link ◽  
Hydraulic Cylinders ◽  
Load Characteristics

To control a movement speed of the output link of an executive hydraulic engine (hydraulic cylinder or hydraulic motor), volumetric hydraulic drives traditionally use volumetric and throttle control methods. Under volumetric control, a supply unit employs a pressure-regulated positive displacement pump, as a result of which it is impossible or difficult to separate and independently control the movement speed of the output links of the hydraulic cylinders. In case of throttle control, there is a significant dependence of the speed of the output link on the load it overcomes, a low efficiency of the hydraulic drive and hereto related active heating of the working fluid, as well as large energy losses. However, in embodiment, due to lack of an expensive variable pump, this method of control is much cheaper and can be used in a multi-channel hydraulic drive with a centralized supply unit.Depending on the throttling device localization in the hydraulic drive circuit, there are series (primary or secondary control) and parallel (working fluid bypass adjustment) throttle connection schemes. The secondary control scheme, which generates a pressure in the outlet of the executive hydraulic engine, is preferable due to the fact that it provides an increased pressure in both cavities of the executive hydraulic engine and, accordingly, a lack of combined air bubbles in the working fluid. Heat released in the throttle is discharged directly into the tank, and the pressure in the outlet reduces the danger level of the emergency situation consequences in the event of an unauthorized change in the sign of the load to be overcome. The quality of control is, mainly, assessed by the type of load characteristics, i.e. dependences of the output link speed and its developed power on the load to be overcome, as well as by the control efficiency (the total efficiency value of the regulating and executive subsystems of the hydraulic drive). The dependence of the dynamics and kinematics of the hydraulic drive on the control methods are of particular interest.The proposed paper, based on the developed mathematical models and their testing for specific sizes of hydraulic cylinders presents the numerical values of the load characteristics and dependences of the total efficiency on the load value to be overcome. Shows that the speed load characteristic steepness of an executive hydraulic cylinder and the sign of its derivative are determined by the throttle control method. The greatest power developed by the output link of the hydraulic engine is shifted to the loads that are 50 ... 70% of their maximum value.As a result of theoretical studies using numerical calculation methods, a technique has been developed for selecting a throttle control method with an assessment of its quality and efficiency. The results of the conducted studies expand the capabilities to forecast the dynamics and kinematics of the output link of the hydraulic drive at the stage of its engineering design.

Design of a Rotatable One-Element Snake Bone for NOTES

2017 ◽  
Author(s):  
Aoyu Zhang ◽  
Bin Liu ◽  
John Liu ◽  
Tianyu Xie
Keyword(s):  
Degrees Of Freedom ◽  
Cost Effective ◽  
The Body ◽  
Single Element ◽  
Entire Body ◽  
Natural Orifice ◽  
Pass Through ◽  
Bone Structures ◽  
Portal Of Entry ◽  
Novel Design

Over the past decade, natural orifice transluminal endoscopic surgery (NOTES) has developed out of a merger of endoscopy and surgery [1]. NOTES offers the advantages of avoiding external incisions and scars, reducing pain, and shortening recovery time by using natural body orifices as the primary portal of entry for surgeries [2]. The NOTES platform consists of a flexible, hollow body — enabling travel in the interior of the human body — and the distal end (head), the mechanical structure of which is based off of the snake bone. After the distal end passes through a natural orifice, through a transluminal opening of the stomach, vagina, bladder, or colon, and reaches the target working place in the peritoneal cavity, several therapeutic and imaging tools can be passed through the hollow conduit of the NOTES’ body for surgeries [3]. The traditional snake bone design presents two major problems. First, the movement is constrained to two bending degrees-of-freedom (DOF). A need to reorient the tool then often requires the entire body to be rotated by the physician, an unwieldly manipulation that both hinders convenience and results in imprecise control. Second, the traditional fabrication process is tedious and therefore lends to higher manufacturing costs; the bending joints must be first individually machined then assembled together piece-by-piece using rotation pins. We propose a novel design for the snake bone that introduces an additional DOF via rotation and is simple and cost-effective to machine. The revised snake bone design features rotation segments controlled by wires that a physician can readily manipulate for increased control and convenience. Further, because surgical tools that pass through the NOTES body conduit are also installed on snake bone structures, the introduction of rotation to the snake bone design increases each tool’s mobility and manipulation. This advance therefore presents the potential to decrease both the number of required tools and the overall diameter of the NOTES body. Finally, the body is machined as a single element and therefore minimizes the work of assembly.

scholarly journals An active seat suspension design for vibration control of heavy-duty vehicles

2016 ◽  
Vol 35 (4) ◽  
pp. 264-278 ◽  
Author(s):  
Donghong Ning ◽  
Shuaishuai Sun ◽  
Jiawei Zhang ◽  
Haiping Du ◽  
Weihua Li ◽  
...  
Keyword(s):  
Ride Comfort ◽  
Cost Effective ◽  
Basic Structure ◽  
Suspension System ◽  
Heavy Duty ◽  
Linear Motors ◽  
Seat Suspension ◽  
Output Torque ◽  
Hydraulic Cylinders ◽  
Heavy Duty Vehicles

This paper presents the design, fabrication and testing of an innovative active seat suspension system for heavy-duty vehicles. Rather than using conventional linear actuators, such as hydraulic cylinders or linear motors, which need to be well maintained and are always expensive when high force outputs are required, the proposed seat suspension system directly applies a rotary motor in order to provide the required active actuation, without changing the basic structure of the existing off-the-shelf seat suspension. A gear reducer is also applied to amplify the output torque of the motor so that a high output torque can be achieved using a low rated power motor. A static output feedback [Formula: see text] controller with friction compensation is designed to actively reduce seat vibration. Experiments are carried out to test the fabricated suspension prototype. The experimental results show that this type of seat suspension can achieve greater ride comfort in the frequency range of 2–6 Hz than a passive seat suspension. The newly designed active seat suspension is much more cost effective and can be suitable for heavy-duty vehicles.

Novel Design of Biped Robot Using Cable Differential Joint

2012 ◽  
Vol 479-481 ◽  
pp. 2307-2310 ◽  
Author(s):  
Hui Wei ◽  
Mei Shuai ◽  
Zhong Yu Wang
Keyword(s):  
Energy Consumption ◽  
Power Consumption ◽  
Lower Energy ◽  
Humanoid Robot ◽  
Biped Robot ◽  
Peak Torque ◽  
Differential Mode ◽  
Biped Walking ◽  
Human Energy ◽  
Novel Design

In this paper, a novel design of cable differential joint for biped robot is proposed. The transmission of joint is cable and operates in differential mode. Then, cable differential joints are employed to the humanoid robot BHLEG for its torque redistribution, 3-Degree of Freedom (DOF) cable differential joint for hip, one DOF joint for knee, and 2-DOF cable differential joint for ankle. According to the distribution of human energy, torque redistribution of cable differential joint can reduce the power consumption of actuator. Simultaneously, the peak torque and size of actuator is reduced. The aim of this paper is to verify a simplest mechanism for biped walking with lower energy consumption.

Design of a Human Lower Extremity Exoskeleton Prototype

2014 ◽  
Vol 543-547 ◽  
pp. 1510-1514
Author(s):  
Zheng Yao ◽  
Zhi Qiang Li
Keyword(s):  
Control System ◽  
Lower Extremity ◽  
Hydraulic System ◽  
Hardware Design ◽  
Hydraulic Drive ◽  
Drive System ◽  
Exoskeleton Design

A human lower extremity exoskeleton prototype was designed and manufactured, the focus of which is on the hardware design. The object of this exoskeleton design is to help its pilot holding burden. The prototype contains three major modules, the mechanical skeleton, the hydraulic drive system and the control system. The approach and realization progress of each module was explained. Simulation about the hydraulic system was conducted and the result was satisfactory. Multiple actual experiments were applied to the prototype to prove the success of the design.

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