Kinematic modelling of a robotic gait device for early rehabilitation of walking

Rehabilitation of walking is an essential element in the treatment of incomplete spinal cord injured (SCI) patients. During the early post injury period, patients find it challenging to practice upright walking. Simulating stepping movements in a supine posture may be easier and promote earlier rehabilitation. A robotic orthotic device for early intervention in spinal cord injury that does not require the patient to be in an upright posture has been modelled. The model comprises a two-bar mechanical system that is configured and powered to provide limb kinematics that approximate normal overground walking. The modelling work has been based on gait analysis performed on healthy subjects walking at 50 per cent, 75 per cent, and 100 per cent of normal cadence. Simulated angles of hip, knee, and ankle joints show a comparable range of motion (ROM) to the experimental walking data measured in healthy subjects. The model provides operating parameters for a prospective recumbent gait orthosis that could be used in early walking rehabilitation of incomplete SCI patients.     

Unlockable knee joint mechanism for powered gait orthosis

Walking with the knee joint locked increases the amplitude of pelvic tilt and results in an unnatural gait. This paper introduces a powered gait orthosis with a moveable knee joint designed to improve the gait speed of patients with spinal cord injury (SCI). The unlockable knee joint powered gait orthosis (UKJ-PGO) uses a gas spring cylinder and a solenoid locking device to enable flexion of the joint, while the rigidity of the hip-joint device is enhanced using air muscles. A gait analysis was conducted to evaluate the performance of the UKJ-PGO, and the kinematic parameters obtained were compared with those of a standard PGO. In the gait of SCI patients using the UKJ-PGO, the new knee-joint device enabled flexion during the swing phase and showed a decrease in pelvic tilt compared with the standard PGO gait. As greater flexion was possible at the knee joint, the duration of the stance phase substantially decreased to near to the normal value, and the duration of the swing phase increased accordingly. In addition, the gait using the UKJ-PGO was faster than that with the standard PGO.     

Pneumatic interactive gait rehabilitation orthosis: design and preliminary testing

Motor rehabilitation techniques based on passive movement of the lower limbs have been developed over the past 15 years. Gait training automation is the latest innovation in these techniques. This paper describes the design and development of a pneumatic interactive gait rehabilitation orthosis (PIGRO), as well as the first experimental results obtained with healthy subjects. PIGRO consists of a modular and size-adaptable exoskeleton, pneumatic actuation systems for the six actuated degrees of freedom (DoF), and a control unit. The foot orthosis and ankle actuation can be removed and/or replaced with orthopaedic shoes so as to permit gait rehabilitation while advancing between parallel bars with ground contact and partial body weight support (i.e. not walking in place). Control logic provides closed-loop position control independently on each joint, with position feedback for each joint in real time. Imposed curves are physiological joint angles: it is also possible to choose between activating one or both legs and to modify curves to obtain different gait patterns if required. The paper concludes with a presentation of experimental results for the device's performance.     

Analysis of the assistance characteristics for the knee extension motion of knee orthosis using muscular stiffness force feedback

In this paper, we are interested in the characteristics of a knee joint when the knee extension motion was assisted by a powered knee orthosis using a muscular stiffness force feedback. For this purpose, we developed the powered knee orthosis with an artificial pneumatic actuator, which is intended for the assistance and the enhancement of muscular activities of lower limbs. The objective of this study was to confirm the effectiveness of the powered knee orthosis that generated a knee extension torque in the motion related to a knee joint. Twenty healthy subjects participated in this study and their lower limb muscular activities were measured to identify the effectiveness of the powered knee orthosis during sit-to-stand (STS) and squat motion. The muscular activities between with and without assistance of knee extension motion were compared and analyzed for the assistance characteristics of the powered knee orthosis. To generate the knee extension torque, the knee orthosis was controlled using muscular stiffness force (MSF) feedback that is controlled by muscular activities of the vastus intermedius muscle that mainly related to the knee extension motion. For analysis of muscular activities, the surface electromyography of the muscles related to the knee extension motion, i.e., RF, vastus lateralis, vastus medialis and vastus intermedius muscles in lower limbs of the right side were recorded and biodex dynamometer was used to measure the maximal concentric isokinetic strength of the knee extensors. The experimental result showed that muscular activities in lower limbs with the assistance of the powered knee orthosis was reduced by 25.62% in rectus femoris muscle and 29.82% in biceps femoris muscle, respectively and knee extension torque of an knee joint wearing knee orthosis was increased by 17.68% in averaged peak torque. Based on the effectiveness of the powered knee orthosis, weaken elder people may have benefited from the knee extension motion augmented by the powered knee orthosis during activity of daily living, e.g., stair ascent.     

Contributions of the lower extremity joint on the support moment in normal walking and in unexpected step-down walking

ARelative contributions of lower extremity joints on the support moment were investigated in this study Three-dimensional gait analyses were performed in normal walking and in unexpected step-down walking For both gait studies, inverse dynamics were performed to obtain each joint moment of the lower extremity, which was applied to the forward dynamics simulation to determine the contributions on the support moment at different phases of walking The forward dynamic simulation results showed that, in normal walking, the ankle plantar flexois contributed significantly during single-limb-support However, the ankle plantar flexors, knee extensois and hip extensors worked together duimg double-limb-support In unexpected step-down walking, the important contributors on the support of the body during single-limb-support were not only ankle plantar flexors but also knee extensors This study, analyzing the relative contributions of the lower limb joint moments for the body support, would be helpful to understand diffetent unexpected walking conditions and compensatory mechanisms for various pathological gaits     

A feasibility study on the design and walking operation of a biped locomotor via dynamic simulation

A feasibility study on the mechanical design and walking operation of a Cassino biped locomotor is presented in this paper. The biped locomotor consists of two identical 3 degrees-of-freedom tripod leg mechanisms with a parallel manipulator architecture. Planning of the biped walking gait is performed by coordinating the motions of the two leg mechanisms and waist. A threedimensional model is elaborated in SolidWorks® environment in order to characterize a feasible mechanical design. Dynamic simulation is carried out in MSC.ADAMS® environment with the aims of characterizing and evaluating the dynamic walking performance of the proposed design. Simulation results show that the proposed biped locomotor with proper input motions of linear actuators performs practical and feasible walking on flat surfaces with limited actuation and reaction forces between its feet and the ground. A preliminary prototype of the biped locomotor is built for the purpose of evaluating the operation performance of the biped walking gait of the proposed locomotor.     

Design of active orthoses for a robotic gait rehabilitation system

An active orthosis (AO) is a robotic device that assists both human gait and rehabilitation therapy. This work proposes portable AOs, one for the knee joint and another for the ankle joint. Both AOs will be used to complete a robotic system that improves gait rehabilitation. The requirements for actuator selection, the biomechanical considerations during the AO design, the finite element method, and a control approach based on electroencephalographic and surface electromyographic signals are reviewed. This work contributes to the design of AOs for users with foot drop and knee flexion impairment. However, the potential of the proposed AOs to be part of a robotic gait rehabilitation system that improves the quality of life of stroke survivors requires further investigation.     

Intact hip and knee joint moment in coronal plane with unilateral transfemoral amputee

The incidence of osteoarthritis for lower limb amputees, especially unilateral transfemoral amputees, was higher than that of transtibial amputees. Considering level of amputation and bilateral load asymmetry, we could assumed that joint moments in the coronal plane during gait were highly related to the risk of osteoarthritis. Therefore, this study aimed to examine the hip and knee adduction moments in the coronal plane in persons with unilateral transfemoral amputation during walking through gait analysis. The subjects were 12 unilateral transfemoral amputees and 21 healthy persons. Three-dimensional motion analysis was measured bilaterally from 33 persons during walking to calculate temporal-spatial parameters and joint moments. The analysis compared the prosthetic side and the intact side of the amputee group and then analyzed the moment between both the intact sides of the transfemoral amputee group and the healthy persons. The results showed that the intact knee adduction moment of amputees increased by 32% compared to the prosthetic side and more than twice compared to the control group at terminal stance. But the bilateral hip adduction moment was decreased compared to the control group (p<0.05). Therefore it is expected that the higher knee adduction moment on the intact side may cause secondary complication to unilateral transfemoral amputees, but it is difficult to make connection with hip osteoarthritis.     

Design and control of an active artificial knee joint

A passive above knee prosthesis being currently in use does not respond adequately to the needs of daily living activities of an amputee due to its limited functions. Therefore, this study deals with design and testing of an active above knee prosthesis. The essential part of this prosthesis is the knee joint actuator based on active control of basic flexion and extension functions of the knee joint with the motor. The imitation of walking gait pattern by the proposed prosthesis was provided with a trajectory control scheme for the knee joint angle in accordance with the necessity of rule-based control approach.     

A joint normalcy index to evaluate patients with gait pathologies in the functional aspects of joint mobility

Gait analysis using 3D motion capture systems provides joint kinematic and kinetic analysis results such as joint relative angles and moments that can be use used to evaluate the degrees of pathological gait patterns. However, the complex data produced using these 3D motion capture systems can only analyzed by experts, because the gait analysis is highly coupled to the kinematics of each joint. Therefore, several Several previous studies using gait analysis have relied on the data compression technique to represent gait deviation from the average normal profiles as a single value. Even though it is important to evaluate gait pathologies at the joint level, all these previous studies have just used a single value to evaluate the pathological gait pattern. Using just one variable for evaluation of a gait is limited in terms of determining which joint movement patterns are getting better during rehabilitation. Therefore, in this study, a method suitable for evaluating gait deviation during a gait was developed to provide three indices for the hip, knee and ankle joints. In addition, to validate the proposed method in clinical cases, experimental tests were conducted on thirty thirty-six normal walkers and six patients with cerebral palsy. Furthermore, to validate the proposed method in regards to rehabilitation, experimental tests were conducted on three classified walking groups with imposed ankle equinus constraints. The JNI for the hip joint, knee joint and ankle were 8.78 (±3.70), 2.92 (±3.25) and 8.79 (±4.38), respectively, in the normal walking group. However, these values were significantly different for the pathological walking group with cerebral palsy. The JNI of the hip joint, knee joint and ankle joint were 203.73 (±171.59), 81.23 (±52.13) and 248.39 (±149.99), respectively, for this group. There were also differences between any two of the three classified groups with imposed ankle equinus constraints. In particular, the JNI of the ankle joint was statistically different at the p<0.01 level, and this parameter clearly increased as the degree of the imposed ankle equinus was increased. These results demonstrate that the proposed JNI can be used as a scalar factor to evaluate the angular deviation of each joint in normal and patient groups. In addition, this approach can be adapted to evaluate rehabilitation and pre/post surgery.     

Gait generation and change of direction for the underactuated three-legged robot

This paper describes a three-legged robot that consists of one actuated leg and two passive legs. The active leg has a knee joint and an ankle joint. The passive legs have no knee joint, although they have a passive ankle joint respectively. The passive leg part and the actuated leg part are linked by a hip part. The robot behavior is passive while the robot is supported by its passive legs and swings the actuated leg part. Generally, in the event that an actuator or a transmitting mechanism fails, robots cannot apply torques to the joint. We therefore took up a walking robot with passive knee joints not only for the energy-efficient walking but also with a view to making ambulation failsafe in case of mechanical failures.     

Design of a novel knee joint for an exoskeleton with good energy efficiency for load-carrying augmentation

When a linear actuator is used for rotation motion by a knee joint of an exoskeleton, the specifications of the joint range of motion (ROM) and joint torque change according to how the linear actuator are attached. Moreover, while the linear actuator generates a constant amount of force, the joint torque generated by the actuator changes according to the joint angle, which causes the torque contraction. This makes it difficult to meet the required torque and ROM for walk and stand-to-sit and sit-to-stand (STS) motions while carrying a load. To solve these problems we propose a novel knee joint for an exoskeleton with good energy efficiency during walk and STS motions while carrying a load. The mechanism is composed of a four-bar linkage and an elastic element. Based on an analysis of human motion, the design variables of the joint were optimized and the feasibility of the optimized variables was verified through the simulation. The findings from the simulation results suggest that combining a four-bar linkage with a linear actuator allows a large ROM and good torque performance of the knee joint for walk and STS motions. Moreover, the energy efficiency can be improved because the spring mounted parallel to the actuator can store the energy dissipated as negative work and recycle the energy as positive work.     

电动往复式步态矫形器机构优化设计

针对原有往复式步态矫形器对患者体力消耗较大、步态差异大且失真严重、膝关节康复效果微弱等问题,对矫形器进行改进设计,分别在矫形器的髋关节和膝关节处增加了驱动机构,设计出一种电动往复式步态矫形器(Electric reciprocating gait orthosis, ERGO),可通过穿戴在患者下肢上,协助无行走能力的患者实现行走功能。由于人体下肢运动关节的复杂性,电动往复式步态矫形器与人体下肢运动关节不可避免存在一定的差异,因此需要通过机构的优化使得人-机之间髋、膝关节的运动规律及下肢末端轨迹更加接近,从而避免患者在使用过程中由于人-机运动偏差而造成不必要的伤害。在此基础上通过仿真分析和试验验证,证明了电动式往复式步态矫形器的可行性和优化结果的有效性。     

双足机器人腿部新构型设计与试验研究

探究高动态性能双足机器人对腿部设计的要求,阐明机器人腿部设计准则、设计方案和实现措施。提出一种腿部串并联新构型方案,膝关节驱动器上移到髋关节,踝关节驱动器上移到膝关节,膝关节驱动器通过简化五连杆机构将运动传递到膝部,踝关节驱动器通过并联四连杆机构将运动传递到踝部。对踝关节并联机构和整个腿部关节进行运动学正逆解,建立新构型机器人的仿真模型。考虑运动控制算法,完成机器人动力学仿真。测试准直驱驱动器性能,并完成串并联构型腿部样机试验验证,机器人可实现0.4m/s的行走速度。结果表明,提出的腿部串并联新构型与传统串联构型比具有更高的运动性能,新构型机器人性能在真机测试中得到验证。该串并联新构型方案在双足机器人和其它服务机器人领域具有广阔的应用前景。     

教学型双足步行机器人转向步态规划方法的研究

双足机器人的步态规划包括直线行走和转向两个部分。在直线行走中,髋关节偏转的自由度被限制,而在转向过程中,最终的转向则必须通过髋关节的偏转才能实现。针对双足机器人转向时的步态规划问题,利用关节转向角进行多项式插值的方法,对机器人转向时的步态进行了规划。通过MATLAB和ADAMS建立虚拟样机,对步态规划结果进行仿真,仿真结果验证了步态规划的正确性。     

教学型双足步行机器人直线行走步态稳定规划方法

通过对双足机器人行走步态的研究,利用多项式插值法对双足机器人直线行走步态进行规划,分析了踝关节轨迹和髋关节轨迹,通过调节单腿支撑期和双腿支撑期的比例系数来调整机器人的行走步态,使其实现稳定步行。再通过ADAMS建立虚拟样机仿真实验,验证了这种步态规划方法的正确性与可行性。     

橡胶节点对全主动液压减振器的影响

液压减振器两端橡胶节点能够保护作动器的安全,但其参数会对减振器的性能产生很大影响。将节点等效成并联的弹簧阻尼系统,建立了作动器橡胶节点的动力学模型,理论分析了节点刚度以及作动频率对作动力滞后相位的影响。充分考虑液压阀和负载的影响,利用SIMPACK和MATLAB建立了液压作动器和车辆系统的联合仿真模型,并对不同节点刚度的情况进行了仿真分析。结果表明:对于较低的工作频带,节点刚度对实际输出到车体上的作动力影响不大,但会造成作动器活塞杆的作动位移产生很大差异。最后,给出了实际应用中合理选择橡胶节点参数的建议。     

Gait Planning for a Quadruped Robot with One Faulty Actuator

Fault tolerance is essential for quadruped robots when they work in remote areas or hazardous environments. Many fault-tolerant gaits planning method proposed in the past decade constrained more degrees of freedom(DOFs) of a robot than necessary. Thus a novel method to realize the fault-tolerant walking is proposed. The mobility of the robot is analyzed first by using the screw theory. The result shows that the translation of the center of body(Co B) can be kept with one faulty actuator if the rotations of the body are controlled. Thus the DOFs of the robot body are divided into two parts: the translation of the Co B and the rotation of the body. The kinematic model of the whole robot is built, the algorithm is developed to actively control the body orientations at the velocity level so that the planned Co B trajectory can be realized in spite of the constraint of the faulty actuator. This gait has a similar generation sequence with the normal gait and can be applied to the robot at any position. Simulations and experiments of the fault-tolerant gait with one faulty actuator are carried out. The Co B errors and the body rotation angles are measured. Comparing to the traditional fault-tolerant gait they can be reduced by at least 50%. A fault-tolerant gait planning algorithm is presented, which not only realizes the walking of a quadruped robot with a faulty actuator, but also efficiently improves the walking performances by taking full advantage of the remaining operational actuators according to the results of the simulations and experiments.     

套装式助力机器人动力学建模与仿真

针对老年人或者下肢功能较弱患者自主行走存在一定困难的问题,研究了一种能够辅助其行走的套装式助力机器人.机器人工作时绑缚在人体上,为行走提供动力.机器人左右对称,单侧机构包括髋关节和膝关节两部分,分别由直流电机驱动丝杠螺母机构的电动缸实现.基于Matlab/Simulink和SimMechanics建立了套装式助力机器人...     

Effect of Radial Clearance on Wear and Contact Pressure of Hard-on-Hard Hip Prostheses Using Finite Element Concepts

Wear of the bearing surface increases the revision rate of artificial hip replacements and is influenced by the radial clearances between the acetabulum cup and the femoral head. The objective of this article is to determine the effect of various radial clearance values over the contact pressure and wear of the hard-on-hard—that is, polycrystalline diamond (PCD)—hip prostheses using finite element concepts for normal walking conditions. The wear of the hip bearing surface is determined by considering the contact pressures obtained from the hip gait instants of normal walking activity and sliding distance determined from the three-dimensional hip gait motions. The radial clearance value of 0.05 mm showed less volumetric wear rate when compared with other radial clearance values. Overall, it is recommended that the low radial clearance between the contacting pair is suitable for PCD-on-PCD hip prostheses.