Mechanical Leg Research Articles

Trajectory planning of a novel lower limb rehabilitation robot for stroke patient passive training

A new applicable sitting/lying lower limb rehabilitation robot is proposed to help stroke patients. It can realize the sitting/lying training postures to fit people in all the rehabilitation stages. Based on the modularization design, the movable seat can be separated from and grouped into the lower limb rehabilitation robot, which is convenient for patients to sit down. As the most important part of lower limb rehabilitation robot, the mechanical leg design theory is introduced in detail. According to the physician clinical suggestions, a new trajectory planning method is proposed based on the dual quartic polynomial interpolation method. It could realize the adjustment of each joint maximum velocity during the training on account of patient recovery. The accelerations of the joints at target position equal zero, which will reduce impact loads on the patients damaged leg. Also, the dwell time the joints staying at the target angular positions can be increased. Those advantages make the lower limb rehabil...

No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation.

Patient-specific instrumentation (PSI) uses 3D preoperative imaging to produce individualized cutting blocks specific to patients' anatomy and according to the preoperative plan with the aim to reduce the number of mechanical leg alignment (MLA) outliers, to improve implant positioning and to decrease surgery time. The primary purpose of this study was to investigate the efficacy of a specific PSI in comparison with standard instrumentation (SI) in reducing the number of MLA outliers. It was hypothesized that the number of MLA outliers would be significantly lower in the PSI group. A multicenter randomized controlled trial was implemented. There were 59 patients in the PSI group and 66 in the SI group. The absolute number of outliers outside the ± 3° target neutral MLA was compared between the groups with a Chi-square test. As secondary outcomes, the Knee Society Score (KSS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were compared between the groups preoperatively and at 90-day follow-up. There were 15 (26.3%) MLA outliers in the PSI group and 8 (12.3%) in the SI group. The number of outliers was not independent from the group ( X2 (1) = 3.8, p = 0.04; Relative risk = 1.5). Preoperatively, there were no significant differences between the groups when comparing their KSS and KOOS sub-scores. At 90 days postoperatively, the patients in the SI group showed better KOOS-Quality of Life (KOSS-QOL) in comparison with the PSI group (p < 0.0001). The use of PSI did not significantly reduce the number of MLA outliers in comparison with SI. There were no differences when comparing the achieved mean MLA of both groups. Level I, prospective randomized controlled trial.

Tourniquet application during TKA did not affect the accuracy of implant positioning: a randomized clinical trial.

The accuracy of the identification of anatomical landmarks with versus without tourniquet application and its effect on implant positioning remained unknown. Therefore, the hypothesis of the present study was that tourniquet application did not affect the accuracy of the reconstruction of the mechanical leg alignment, the joint line level, and the patellar height. The prospective randomized monocentric trial (Clinical-Trials.gov NCT02475603) included a total of 86 patients scheduled to undergo primary TKA. The patients were allocated to receive TKA with (Group A, n = 43) or without tourniquet (Group B, n = 43). The mechanical leg alignment, the joint line level (modified Kawamura), and the patellar height (Plateau-patella angle, Insall Salvati index, and modified Insall Salvati index) were measured pre- and postoperatively on standardized calibrated digital radiographs. Mean, SEM, median, range, and p value were calculated for each parameter. There was no statistical difference between the groups with regard to demographics, preoperative deformity, implant design, and surgical technique (n.s.). The mechanical leg alignment, the joint line level, and the patellar height revealed, in both groups, similar results pre- and postoperatively (n.s.). The mechanical leg alignment, the joint line level, and the patellar height could be accurately reconstructed with and without tourniquet use. With respect to clinically relevant surrogate parameters of implant positioning, TKA can safely be performed without a tourniquet. Available data do not support a routine use of tourniquet during TKA and might justify a change of the clinical pathway. Level I.

Robotic Leg Design to Analysis the Human Leg Swing from Motion Capture

In this paper presented the prototype of robotic leg has been designed, constructed and controlled. These prototype are designed from a geometric of human leg model with three joints moving in 2D plane. Robot has three degree of freedom using DC servo motor as a joint actuators: hip, knee and ankle. The mechanical leg constructed using aluminum alloy and acrylic material. The control movement of this system is based on motion capture data stored on a personal computer. The motions are recorded with a camera by use of a marker-based to track movement of human leg. Propose of this paper is design of robotic leg to present the analysis of motion of the human leg swing and to testing the system ability to create the movement from motion capture. The results of this study show that the design of robotic leg was capable for practical use of the human leg motion analysis. The accuracy of orientation angles of joints shows the average error on hip is 1.46º, knee is 1.66º, and ankle is 0.46º. In this research suggesting that the construction of mechanic is an important role in the stabilization of the movement sequence.

Multibody dynamics modeling of electromagnetic direct-drive vehicle robot driver

Collaborative dynamics modeling of flexible multibody and rigid multibody for an electromagnetic direct-drive vehicle robot driver is proposed in the article. First, spatial dynamic equations of the direct-drive vehicle robot driver are obtained based on multibody system dynamics. Then, the shift manipulator dynamics model and the mechanical leg dynamics model are established on the basis of the multibody dynamics equations. After establishing a rigid multibody dynamics model and conducting finite element mesh and finite element discrete processing, a flexible multibody dynamics modeling of the electromagnetic direct-drive vehicle robot driver is established. The comparison of the simulation results between rigid and flexible multibody is performed. Simulation and experimental results show the effectiveness of the presented model of the electromagnetic direct-drive vehicle robot driver.

Fuzzy-neural-network-based speed control method and experiment verification for electromagnetic direct drive robot driver

Vehicle test has a great significance for the development of new vehicle products. It is necessary for a new type of vehicle stereotypes to conduct a lot of vehicle test. Some vehicle test, such as emission durability test, vehicle performance test, vehicle noise test, high and low temperature environment test, vehicle road test, vehicle bench test, is more suitable for the operation by robot. Robot driver is an intelligent robot that can realize automatic driving under harsh environment in vehicle test instead of a human driver without any modification. Because of the vehicle is not required to be modified, and the vehicle robot driver can be directly installed in the different vehicle cab. The drive way of the vehicle robot driver includes the hydraulic drive, the pneumatic drive and the servo electric drive. The hydraulic drive is steady, but it needs an oil cylinder. It is not easy for the pneumatic drive to accurate positioning and the real-time property. As a driving device of the robot driver, the servo electric drive needs a mechanism of rotary motion into linear motion. Electromagnetic linear motor can solve the shortcomings of three other drive styles. It can improve the transmission efficiency and transmission accuracy, and make the transmission mechanism simple. A control approach of speed in an electromagnetic direct drive robot driver based on fuzzy neural network is proposed in this paper, in order to realize the accurate speed tracking of different driving test cycle conditions. The electromagnetic direct drive robot driver adopts an electromagnetic linear actuator as the driving device in this paper. The throttle mechanical leg, the brake mechanical leg, the clutch mechanical leg and the shift manipulator are directly driven through the electromagnetic linear actuator. The control system structure and the coordinated motion control model of the electromagnetic direct drive robot driver are given. On the basis of this, the speed control model based on fuzzy neural network of the electromagnetic direct drive robot driver is designed. The shift manipulator displacement, the throttle mechanical leg displacement, the clutch mechanical leg displacement and the brake mechanical leg are the input variables of the fuzzy neural network model, and the vehicle speed of the test vehicle is the output variable of the fuzzy neural network model. The number of the input variable membership functions is three, and the type of the input variable membership functions is gbellmf. The fuzzy neural network training algorithm adapts the hybrid learning algorithm combing with back propagation algorithm and least square method. The proposed control method of the electromagnetic direct drive robot driver is experimentally proved and compared with other control methods and with human driver performances. Actual vehicle test results and error comparison analysis show that the vehicle speed tracking accuracy of robot driver using the proposed approach is higher than that of robot driver using PID control method and human driver. Besides, the proposed method has good adaptability under all kinds of driving test cycle, which can ensure the accuracy and effectiveness of vehicle test.

Measurement of lower limb alignment: there are within-person differences between weight-bearing and non-weight-bearing measurement modalities

Purpose Previous studies have compared weight-bearing mechanical leg axis (MLA) measurements to non-weight-bearing measurement modalities. Most of these studies compared mean or median values and did not analyse within-person differences between measurements. This study evaluates the within-person agreement of MLA measurements between weight-bearing full-length radiographs (FLR) and non-weight-bearing measurement modalities (computer-assisted surgery (CAS) navigation or MRI).Materials and methodsTwo independent observers measured the MLA on pre- and postoperative weight-bearing FLR in 168 patients. These measurements were compared to non-weight-bearing measurements obtained by CAS navigation or MRI. Absolute differences in individual subjects were calculated to determine the agreement between measurement modalities. Linear regression was used to evaluate the possibility that other independent variables impact the differences in measurements.ResultsA difference was found in preoperative measurements between FLR and CAS navigation (mean of 2.5° with limit of agreement (1.96 SD) of 6.4°), as well as between FLR and MRI measurements (mean of 2.4° with limit of agreement (1.96 SD) of 6.9°). Postoperatively, the mean difference between MLA measured on FLR compared to CAS navigation was 1.5° (limit of agreement (1.96 SD) of 4.6°). Linear regression analysis showed that weight-bearing MLA measurements vary significantly from non-weight-bearing MLA measurements. Differences were more severe in patients with mediolateral instability (p = 0.010), age (p = 0.049) and ≥3° varus or valgus alignment (p = 0.008).ConclusionThe clinical importance of this study lies in the finding that there are within-person differences between weight-bearing and non-weight-bearing measurement modalities. This has implications for preoperative planning, performing total knee arthroplasty (TKA), and clinical follow-up after TKA surgery using CAS navigation or patient-specific instrumentation.Level of evidenceIII.

Research on Safety and Compliance of a New Lower Limb Rehabilitation Robot.

The lower limb rehabilitation robot is an application of robotic technology for stroke people with lower limb disabilities. A new applicable and effective sitting/lying lower limb rehabilitation robot (LLR-Ro) is proposed, which has the mechanical limit protection, the electrical limit protection, and the software protection to prevent the patient from the secondary damage. Meanwhile, as a new type of the rehabilitation robots, its hip joint rotation ranges are different in the patient sitting training posture and lying training posture. The mechanical leg of the robot has a variable workspace to work in both training postures. So, if the traditional mechanical limit and the electrical limit cannot be used in the hip joint mechanism design, a follow-up limit is first proposed to improve the compatibility of human-machine motion. Besides, to eliminate the accident interaction force between the patient and LLR-Ro in the process of the passive training, an amendment impedance control strategy based on the position control is proposed to improve the compliance of the LLR-Ro. A simulation experiment and an experiment with a participant show that the passive training of LLR-Ro has compliance.

Software and instrument improvements reduced significantly navigation acquisition time in computer assisted TKA: A cadaveric study

Purpose: Computer navigation in total knee arthroplasty (TKA) has proven to significantly reduce the number of outliers in prosthesis positioning and to improve mechanical leg alignment. Despite th...

Development of a wearable exoskeleton rehabilitation system based on hybrid control mode

Lower limb rehabilitation exoskeletons usually help patients walk based on fixed gait trajectories. However, it is not suitable for unilateral lower limb disorders. In this article, a hybrid training mode is proposed to be applied in rehabilitation for unilateral lower limb movement disorders. The hybrid training includes two modes, that is, the passive training mode and the active assist mode. At an early stage of the rehabilitation therapy, the passive training mode is utilized, in which microelectromechanical systems-based attitude and heading reference system is used to collect the gait trajectory of the healthy limb. The exoskeleton on the unhealthy limb will be driven to track the joint trajectory of the healthy limb. If the patient’s abilities recovered, the rehabilitation system can be switched to the active assist mode. Two force sensors are imbedded into the interface on the thigh to measure the interaction information in order to detect the patient’s initiative walking intention. In the active mode, the walking gait trajectory is modified and generated based on the gait trajectory of the healthy side via the attitude and heading reference system. In this article, a position close control loop is designed to drive the mechanical leg to help the unhealthy limb walk. Laboratory experiments are performed on a healthy human subject to illustrate the proposed approach. Experimental results show that the proposed method can be applied and extended in the passive and active rehabilitation mode for the unilateral lower limb disorders.

The Mid-Term Outcome of Total Knee Arthroplasty in Patients With Prior High Tibial Osteotomy: A Prospective Study

Background: It is generally accepted that total knee arthroplasty (TKA) after high tibial osteotomy (HTO) is technically more difficult; however, there is still disagreement whether the subsequent arthroplasty is compromised. Objectives: The current case series study aimed to assess patients treated by knee arthroplasty after a previous high tibial osteotomy and to determine the influence of this osteotomy on the clinical and radiologic outcomes of subsequent arthroplasty. Methods: Up to April 2013, twenty-three patients with a history of twenty-five proximal tibial osteotomies prior to TKA were identified and compared with a matched group who underwent primary TKA in Shafa Orthopedic Hospital, Tehran, Iran. Demographic parameters of patients, surgical details, the knee range of motion (ROM), and American functional knee society (AKS) scores before and after TKA were recorded in the HTO and control groups. Weight bearing alignment radiographs were taken preoperatively and at the last follow-up. At the latest visit, patients’ satisfaction was recorded. Results: After an average of 49 months follow-up, all patients in the HTO and control groups were satisfied with their current level of function. In the HTO group, the rectus snip had to be used for better exposure in eight cases. There was no statistically significant difference between the two groups in postoperative knee ROM, mechanical leg alignment and mean functional knee society score, but the mean of operation time in the HTO group was significantly longer than that of the TKA time in the control group. Conclusion: Although knee arthroplasty after HTO is technically more challenging than a primary procedure, the results of clinical scores, postoperative ROM and radiological evaluation in the study subjects were comparable with those of the primary TKA in midterm follow-up. Rectus snip is a safe procedure in such difficult cases for better exposure.

Development of an innovative sandwich composite material for protection of lower limb against landmine explosion: mechanical leg test results

This paper includes results of the blast tests which were performed with the aim of comparing the energy absorption and protection efficiency of protective boots with different sole configurations. Tests were performed on a mechanical leg model vestured with protective boots. Load and three axis acceleration values were measured during the blast tests to determine the protection efficiency of boot samples. Herewith, it was understood that merely a monolithic composite layer used in a sole does not provide protection, whereas compressible metallic honeycomb material-based sandwich composites demonstrate better energy absorption. With the innovative sandwich composite material developed in this study, energy absorption was increased by 209% in comparison to monolithic composites.

Functional ligament-guided femoral rotation with patient-specific instruments: description of a new surgical technique

Background: There are two basic implantation philosophies in total knee arthroplasty that essentially determine the rotational alignment of the femur. One method, the measured resection technique, uses bony landmarks to determine alignment, while the other, the gap-balancing technique, uses soft-tissue tension as the reference. The use of patient-specific instrumentation (PSI) has so far only been employed in cases where alignment is based on bony landmarks; alignment of the femoral rotation applying the gap-balancing technique is not currently possible. Methods: This paper describes the use of PSI with alignment using a balancer device in 25 patients, corresponding to the gap-balancing technique. The average age of the study population was 67.6±6.7 yr. The Knee Society Score (KSS) and flexion of the knee joint were recorded preoperatively and then at 3 and 12 mo postoperatively. Postoperatively, function was determined based on the Forgotten Joint Score (FJS), and any complications were documented. Deviation to the neutral mechanical leg axis also was determined based on long-standing radiographs of the lower extremity. Results: The KSS and flexion improved after 3 and 12 mo compared with preoperative results. The FJS was 34.4±4.2 points after 3 mo and 57.8±8.4 points after 12 mo. There were no complications. The deviation of the neutral mechanical axis averaged 1.5 degrees±1.8 degrees. Conclusions: The data show that the alignment of the PSI also can be achieved functionally, which will extend the range of application of PSI, especially in complex anatomical situations and after previous surgery.

Knee joint distraction compared with high tibial osteotomy: a randomized controlled trial

PurposeBoth, knee joint distraction as a relatively new approach and valgus-producing opening-wedge high tibial osteotomy (HTO), are knee-preserving treatments for knee osteoarthritis (OA). The efficacy of knee joint distraction compared to HTO has not been reported.MethodsSixty-nine patients with medial knee joint OA with a varus axis deviation of <10° were randomized to either knee joint distraction (n = 23) or HTO (n = 46). Questionnaires were assessed at baseline and 3, 6, and 12 months. Joint space width (JSW) as a surrogate measure for cartilage thickness was determined on standardized semi-flexed radiographs at baseline and 1-year follow-up.ResultsAll patient-reported outcome measures (PROMS) improved significantly over 1 year (at 1 year p < 0.02) in both groups. At 1 year, the HTO group showed slightly greater improvement in 4 of the 16 PROMS (p < 0.05). The minimum medial compartment JSW increased 0.8 ± 1.0 mm in the knee joint distraction group (p = 0.001) and 0.4 ± 0.5 mm in the HTO group (p < 0.001), with minimum JSW improvement in favour of knee joint distraction (p = 0.05). The lateral compartment showed a small increase in the knee joint distraction group and a small decrease in the HTO group, leading to a significant increase in mean JSW for knee joint distraction only (p < 0.02).ConclusionCartilaginous repair activity, as indicated by JSW, and clinical outcome improvement occurred with both, knee joint distraction and HTO. These findings suggest that knee joint distraction may be an alternative therapy for medial compartmental OA with a limited mechanical leg malalignment.Level of evidenceRandomized controlled trial, Level I.

Hierarchical Coordinated Control Method for Unmanned Robot Applied to Automotive Test

The paper describes application of unmanned robot applied to automotive test (URAT) to save time, costs, and to improve accuracy of tests. A hierarchical coordinated control method based on fuzzy logic theory is proposed for URAT, to realize the coordinated control and the accurate speed tracking of driving test cycle during all kinds of conditions. The system structure is briefly described in the paper. Similar to a skilled human driver, a control method based on Saridis hierarchical architecture to coordinate multiple robot manipulators systems for the automotive test system is presented. The coordinated movements for throttle mechanical leg, clutch mechanical leg, brake mechanical leg are designed. On top of that, the fuzzy speed controller for URAT is used to accurately track the desired vehicle velocity under different test conditions. Experiments have been conducted by using a Ford FOCUS car. The proposed control method of URAT is experimentally proved and compared with other control methods and with human driver performances.

Computer-assisted total knee arthroplasty using mini midvastus or medial parapatellar approach technique: A prospective, randomized, international multicentre trial.

BackgroundDespite the growing evidence in the literature there is still a lack of consensus regarding the use of minimally invasive surgical technique (MIS) in total knee arthroplasty (TKA).MethodsA prospective, randomized, international multicentre trial including 69 patients was performed to compare computer-assisted TKA (CAS-TKA) using either mini-midvastus (MIS group) or standard medial parapatellar approach (conventional group).Patients from 3 centers (Maastricht, Zwickau, Adelaide) with end-stage osteoarthritis of the knee were randomized to either an MIS group with dedicated instrumentation or a conventional group to receive cruciate retaining CAS-TKA without patella resurfacing. The primary outcome was to compare post operative pain and range of motion (ROM). The secondary outcome was to measure the duration of surgery, blood loss, chair rise test, quadriceps strength, anterior knee pain, Knee Society Score (KSS),WOMAC scores, mechanical leg axis and component alignment.ResultsPatients in the MIS group (3.97 ± 2.16) had significant more pain at 2 weeks than patients in the conventional group (2.77 ± 1.43) p = 0.003. There was no significant difference in any of the other primary outcome parameters. Surgery time was significantly longer (p < 0.001) and there were significantly higher blood loss (p = 0.002) in the MIS group as compared to the conventional group. The difference of the mean mechanical leg alignment between the groups was not statistically significant (–0.43° (95 % CI –1.50 – 0.64); p = 0.43).There was no significant difference of component alignment between the two surgical groups with respect to flexion/extension (p = 0.269), varus/valgus (p = 0.653) or rotational alignment (p = 0.485) of the femur component and varus valgus alignment (p = 0.778) or posterior slope (p = 0.164) of the tibial component.ConclusionThere was no advantage of the MIS approach compared to a conventional approach CAS-TKA in any of the primary outcome measurements assessed, however the MIS approach was associated with longer surgical time and greater blood loss. MIS-TKA in combination with computer navigation is safe in terms of implant positioning.Trial registration numberClinicalTrials.gov NCT02625311 8 December 2015

Innovative Design and Performance Evaluation of a High-speed Bionic Mechanical Leg

For most legged robots the drive-motors are mounted on the joints of legs, which increase leg's mass and rotary inertia. When mounted on legs, the drive-motor has to rotate clockwise and anticlockwise periodically to swing a leg back and forth. Larger inertia of the leg, as well as the ever-changing status of frequent acceleration and deceleration of the motors, limits the moving speed of the legged robots. This article proposes an improved mechanical design to overcome such problems. All the drive-motors are installed on the robot body to reduce the rotary inertia of the legs. Then a crank-rocker mechanism is used to transform continuous rotation of motors to back and forth motion of the leg. With this scheme, the motor may reach higher rotation speed since it drives a lighter leg with no change of the rotation direction. In addition, an elastic tendon is attached to the ankle to reduce the pulse stress on the leg. Kinematics and dynamics analysis demonstrates that the new design enlarges end-workspace, reduces driving torque and increases ground reaction force, which means the new robot has lager stride and higher swing frequency of leg to achieve faster moving.

Fuzzy neural network–based shift control method of electromagnetic unmanned robot applied to automotive test

A new shift control method for an electromagnetic unmanned robot applied to automotive test based on a Sugeno fuzzy neural network is proposed in this article. The method can achieve the intelligent shifting of unmanned robot applied to automotive test with good robustness. The structure and working principle of the electromagnetic unmanned robot applied to automotive test are discussed. The electromagnetic unmanned robot applied to automotive test adopts electromagnetic linear motors as its drive mechanism. The position of the throttle mechanical leg for the electromagnetic unmanned robot applied to automotive test, the speed and acceleration of the test vehicle are used as the input to the Sugeno fuzzy neural network model, and the shifting of the test vehicle is used as the output of the Sugeno fuzzy neural network model. The number of membership functions is three, and the type of membership functions is gbellmf (generalized bell membership function). The hybrid learning algorithm that combines the back propagation algorithm with a least square method is applied to train and optimize the network parameters, and the optimal network parameters are determined. According to the optimized network parameters and the model input parameters, the intelligent shifting of the electromagnetic unmanned robot applied to automotive test is completed with the Sugeno fuzzy neural network. An electromagnetic unmanned robot applied to automotive test prototype is designed and manufactured. Experiments have been conducted using a Ford FOCUS car. The proposed control method is verified by the continuous and stable shift operation of the electromagnetic unmanned robot applied to automotive test prototype.

Design of prototype simulation system for driving performance of electromagnetic unmanned robot applied to automotive test

Purpose – The purpose of this paper is to present a prototype simulation system for driving performance of an electromagnetic unmanned robot applied to automotive test (URAT) to solve that it is difficult and dangerous to online debug control program and to quickly obtain test vehicle dynamic performance. Design/methodology/approach – The driving performance of the electromagnetic URAT can be evaluated by the prototype simulation system. The system can simulate various driving conditions of test vehicles. An improved vehicle longitudinal dynamics model matching to the electromagnetic URAT is established. The proposed model has good real-time, and it is easy to implement. The displacement of throttle mechanical leg, brake mechanical leg, clutch mechanical leg and shift mechanical arm is used for the system input. Test vehicle speed and engine speed are used for the system output, and they are obtained by the computation of the established vehicle longitudinal dynamics model. Findings – Driving conditions simulation test and vehicle emission test are performed using a Ford Focus car. Simulation and experiment results show that the proposed prototype simulation system in the paper can simulate the driving conditions of actual vehicles, and the performance that electromagnetic URAT drives an actual vehicle is evaluated by the simulation system. Research limitations/implications – Future research will focus on improving the real time of the proposed simulation system. Practical implications – The autonomous driving performance of electromagnetic URAT can be evaluated by the proposed prototype simulation system. Originality/value – A prototype simulation system for driving performance of an electromagnetic URAT based on an improved vehicle longitudinal dynamics model is proposed in this paper, so that it can solve the difficulty and danger of online debugging control program, quickly obtaining the test vehicle performance.

The Reliability Analysis of Mechanical Leg (2UPS+UP) Based on a Discrete Time Repairable Markov Model

We have analyzed some reliability problems of the 2UPS+UP mechanism using continuous Markov repairable model in our previous work. According to the check and repair of the robot is periodic, the discrete time Markov repairable model should be more appropriate. Firstly we built up the discrete time repairable model and got the one step transition probability matrix. Secondly solved the steady state equations and got the steady state availability of the mechanical leg, by the solution of the difference equations the reliability and the mean time to first failure were obtained. In the end we compared the reliability indexes with the continuous model.