scholarly journals An approach to drastically reduce the required legs DOFs for bipedal robots and lower-limb exoskeletons

Robotica ◽  
2021 ◽  
pp. 1-15
Author(s):  
Rodrigo S. Jamisola ◽  
Rodney G. Roberts
Keyword(s):  
Relative Motion ◽  
Lower Limb ◽  
Degrees Of Freedom ◽  
Reference Frames ◽  
Null Space ◽  
Usual Method ◽  
Bipedal Walking ◽  
Basic Form ◽  
Bipedal Robots ◽  
Fixed Reference

Abstract We present a method to drastically reduce the required number of degrees-of-freedom (DOFs) needed for walking for each leg of bipedal robots and lower-limb exoskeletons. This approach releases more legs DOFs in the null space to do other tasks, instead of unnecessarily constraining them. It uses relative reference frames to control relative motion between the two feet, instead of the usual method of controlling foot movement with respect to fixed reference frames. In its basic form, it controls the bipedal walking holistically using two controllers: (1) world space control using relative feet motion and (2) null-space control of the legs posture.

Using K’NEX to Understand and Teach Concepts in Movement Biomechanics

2010 ◽  
Author(s):  
Steven Charles
Keyword(s):  
Lower Limb ◽  
Reference Frames ◽  
Human Motion ◽  
The Body ◽  
Single Degree Of Freedom ◽  
Generalized Coordinates ◽  
Single Degree ◽  
Fixed Reference ◽  
Time To Learn ◽  
And Robotics

In order to analyze the kinematics or model the dynamics of human motion, one must be able to abstract from the intricate anatomy of the body the mechanical linkages and kinematic constraints which best approximate the joints of the body. Given the number and complexity of joints in the human body, this abstraction can be a challenging task, especially for students. While rotations about a single degree of freedom are easy to grasp, rotations about multiple DOF, which occur commonly throughout the body (e.g. shoulder, wrist, ankle, etc.) are anything but trivial. Likewise, the kinematics or dynamics of mechanical linkages such as the upper or lower limb quickly become unwieldy. To deal with these challenges, students learn to use tools from mechanics and robotics (body- and space-fixed reference frames, transformations, generalized coordinates, etc.), but these concepts can themselves be challenging and certainly take time to learn.

BIPED ROBOT DESIGN WITH VARIABLE ANKLE STIFFNESS

2017 ◽  
Vol 17 (07) ◽  
pp. 1740013 ◽  
Author(s):  
XIZHE ZANG ◽  
ZHENKUN LIN ◽  
XINRAN SUN ◽  
YIXIANG LIU
Keyword(s):  
Energy Loss ◽  
Degrees Of Freedom ◽  
Sagittal Plane ◽  
Variable Stiffness ◽  
Biped Robot ◽  
Lower Limbs ◽  
Bipedal Walking ◽  
Bipedal Robots ◽  
Ankle Stiffness ◽  
Ground Impact

Human lower limbs have particular flexibility. Both the efficiency of bipedal walking and the ability to protect actuators with low energy loss are worthy references for the design of bipedal robots. This paper proposes a design for a biped robot with joints of variable stiffness. The robot has three degrees of freedom in the sagittal plane in each leg. The hips and knees are driven directly by the motor, while the ankles are passive joints with adjustable stiffness. After a comprehensive investigation, a variable stiffness mechanism was introduced based on lever principles, and driven by a motor that can realize real-time adjustment. Simulations verified the necessity of variable stiffness joints in the robot. The variable stiffness joint can absorb the ground impact on each joint, reduce the energy loss of the motor, and improve the efficiency of movement.

Virtual Geometric Model of the Human Lower Limb

2014 ◽  
Vol 601 ◽  
pp. 193-196
Author(s):  
Lucian Rusu ◽  
Mirela Toth-Taşcău ◽  
Cristian Toader-Pasti
Keyword(s):  
Lower Limb ◽  
Input Data ◽  
Degrees Of Freedom ◽  
Geometric Model ◽  
Normal Range ◽  
Anthropometric Parameters ◽  
Fixed Reference ◽  
Left And Right ◽  
Analysis System ◽  
The Mathematical Model

The aim of this paper is to develop and validate the mathematical model of the human lower limb based on Denavit-Hartenberg (D-H) robotics convention. The proposed geometric model has 7 degrees of freedom (DOF) (3 DOF in hip joint, 2 DOF in knee joint, and 2 DOF in ankle joint). The fixed reference system was placed in the weight centre of the human body. The input data for the model are the angle variations and anthropometric parameters of the lower limb. The angle variations can be defined or imported from a gait analysis system. The anthropometric parameters were introduced from the literature. The model can be adapted to both left and right lower limb. The geometric model was solved in MATLAB environment. The model validation was individually realized taking into account the normal range of motion (ROM) of each joint.

scholarly journals Effects of Dominant and Nondominant Limb Immobilization on Muscle Activation and Physical Demand during Ambulation with Axillary Crutches

2021 ◽  
Vol 6 (1) ◽  
pp. 16
Author(s):  
Kara B. Bellenfant ◽  
Gracie L. Robbins ◽  
Rebecca R. Rogers ◽  
Thomas J. Kopec ◽  
Christopher G. Ballmann
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Weight Bearing ◽  
Lower Limbs ◽  
Medial Gastrocnemius ◽  
Bipedal Walking ◽  
Lower Limb Muscle ◽  
Limb Muscle ◽  
Physical Demand ◽  
Limb Dominance

The purpose of this study was to investigate the effects of how limb dominance and joint immobilization alter markers of physical demand and muscle activation during ambulation with axillary crutches. In a crossover, counterbalanced study design, physically active females completed ambulation trials with three conditions: (1) bipedal walking (BW), (2) axillary crutch ambulation with their dominant limb (DOM), and (3) axillary crutch ambulation with their nondominant limb (NDOM). During the axillary crutch ambulation conditions, the non-weight-bearing knee joint was immobilized at a 30-degree flexion angle with a postoperative knee stabilizer. For each trial/condition, participants ambulated at 0.6, 0.8, and 1.0 mph for five minutes at each speed. Heart rate (HR) and rate of perceived exertion (RPE) were monitored throughout. Surface electromyography (sEMG) was used to record muscle activation of the medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) unilaterally on the weight-bearing limb. Biceps brachii (BB) and triceps brachii (TB) sEMG were measured bilaterally. sEMG signals for each immobilization condition were normalized to corresponding values for BW.HR (p < 0.001) and RPE (p < 0.001) were significantly higher for both the DOM and NDOM conditions compared to BW but no differences existed between the DOM and NDOM conditions (p > 0.05). No differences in lower limb muscle activation were noted for any muscles between the DOM and NDOM conditions (p > 0.05). Regardless of condition, BB activation ipsilateral to the ambulating limb was significantly lower during 0.6 mph (p = 0.005) and 0.8 mph (p = 0.016) compared to the same speeds for BB on the contralateral side. Contralateral TB activation was significantly higher during 0.6 mph compared to 0.8 mph (p = 0.009) and 1.0 mph (p = 0.029) irrespective of condition. In conclusion, limb dominance appears to not alter lower limb muscle activation and walking intensity while using axillary crutches. However, upper limb muscle activation was asymmetrical during axillary crutch use and largely dependent on speed. These results suggest that functional asymmetry may exist in upper limbs but not lower limbs during assistive device supported ambulation.

Effects of Dynamic Model Errors in Task-Priority Operational Space Control

Robotica ◽  
2021 ◽  
pp. 1-12
Author(s):  
Paolo Di Lillo ◽  
Gianluca Antonelli ◽  
Ciro Natale
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Null Space ◽  
Control Algorithms ◽  
Model Errors ◽  
Operational Space ◽  
Dynamic Level ◽  
Concurrent Tasks ◽  
Modeling Errors

SUMMARY Control algorithms of many Degrees-of-Freedom (DOFs) systems based on Inverse Kinematics (IK) or Inverse Dynamics (ID) approaches are two well-known topics of research in robotics. The large number of DOFs allows the design of many concurrent tasks arranged in priorities, that can be solved either at kinematic or dynamic level. This paper investigates the effects of modeling errors in operational space control algorithms with respect to uncertainties affecting knowledge of the dynamic parameters. The effects on the null-space projections and the sources of steady-state errors are investigated. Numerical simulations with on-purpose injected errors are used to validate the thoughts.

scholarly journals Biologically Inspired Design and Development of a Variable Stiffness Powered Ankle-Foot Prosthesis

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Alexander Agboola-Dobson ◽  
Guowu Wei ◽  
Lei Ren
Keyword(s):  
Lower Limb ◽  
Degrees Of Freedom ◽  
Sagittal Plane ◽  
Frontal Plane ◽  
Variable Stiffness ◽  
Plane Motion ◽  
Biologically Inspired ◽  
Passive Rotation ◽  
Ground Conditions ◽  
Biologically Inspired Design

Recent advancements in powered lower limb prostheses have appeased several difficulties faced by lower limb amputees by using a series-elastic actuator (SEA) to provide powered sagittal plane flexion. Unfortunately, these devices are currently unable to provide both powered sagittal plane flexion and two degrees of freedom (2-DOF) at the ankle, removing the ankle’s capacity to invert/evert, thus severely limiting terrain adaption capabilities and user comfort. The developed 2-DOF ankle system in this paper allows both powered flexion in the sagittal plane and passive rotation in the frontal plane; an SEA emulates the biomechanics of the gastrocnemius and Achilles tendon for flexion while a novel universal-joint system provides the 2-DOF. Several studies were undertaken to thoroughly characterize the capabilities of the device. Under both level- and sloped-ground conditions, ankle torque and kinematic data were obtained by using force-plates and a motion capture system. The device was found to be fully capable of providing powered sagittal plane motion and torque very close to that of a biological ankle while simultaneously being able to adapt to sloped terrain by undergoing frontal plane motion, thus providing 2-DOF at the ankle. These findings demonstrate that the device presented in this paper poses radical improvements to powered prosthetic ankle-foot device (PAFD) design.

Cooperation and Null-Space Control of Networked Omni-Directional Mobile Manipulators

2020 ◽  
Author(s):  
Michael John Chua ◽  
Yen-Chen Liu
Keyword(s):  
Degrees Of Freedom ◽  
Null Space ◽  
Kinematic Model ◽  
Mobile Manipulator ◽  
Main Task ◽  
Mobile Manipulators ◽  
Robot Arm ◽  
Task Space ◽  
End Effector ◽  
Mobile Base

Abstract This paper presents cooperation and null-space control for networked mobile manipulators with high degrees of freedom (DOFs). First, kinematic model and Euler-Lagrange dynamic model of the mobile manipulator, which has an articulated robot arm mounted on a mobile base with omni-directional wheels, have been presented. Then, the dynamic decoupling has been considered so that the task-space and the null-space can be controlled separately to accomplish different missions. The motion of the end-effector is controlled in the task-space, and the force control is implemented to make sure the cooperation of the mobile manipulators, as well as the transportation tasks. Also, the null-space control for the manipulator has been combined into the decoupling control. For the mobile base, it is controlled in the null-space to track the velocity of the end-effector, avoid other agents, avoid the obstacles, and move in a defined range based on the length of the manipulator without affecting the main task. Numerical simulations have been addressed to demonstrate the proposed methods.

LOWER LIMB REHABILITATION ROBOT FOR GAIT TRAINING

2014 ◽  
Vol 14 (06) ◽  
pp. 1440004 ◽  
Author(s):  
SHUAI GUO ◽  
JIANCHENG JI ◽  
GUANGWEI MA ◽  
TAO SONG ◽  
JING WANG
Keyword(s):  
Lower Limb ◽  
Degrees Of Freedom ◽  
Balance Training ◽  
Gait Training ◽  
Rehabilitation Robot ◽  
Stroke Patients ◽  
Motion Characteristics ◽  
Set Up ◽  
Limb Rehabilitation ◽  
Lower Limb Rehabilitation

After analyzing the rehabilitation needs of stroke patients and the previous studies on lower limb rehabilitation robot, our lower limb rehabilitation robot is designed for stroke patients' gait and balance training. The robot consists of the mobile chassis, the support column and the pelvis mechanism and it is described in detail. As the pelvis mechanism allows most of the patient's motion degrees of freedom (DOFs), the kinematics model of the mechanism is set up, and kinematics simulation is carried out to study the motion characteristics of the mechanism. After analyzing the calculation and simulation results, the pelvis mechanism is proven to measure up to the movement needs of the paralytic's waist and pelvis in walking rehabilitation process.

scholarly journals Center of Pressure Feedback for Controlling the Walking Stability Bipedal Robots using Fuzzy Logic Controller

2018 ◽  
Vol 8 (5) ◽  
pp. 3678
Author(s):  
Afrizal Mayub ◽  
Fahmizal Fahmizal
Keyword(s):  
Fuzzy Logic ◽  
Degrees Of Freedom ◽  
Fuzzy Logic Controller ◽  
Center Of Pressure ◽  
Bipedal Robots ◽  
Bipedal Robot ◽  
Position Information ◽  
Pressure Feedback ◽  
The Stability ◽  
Foot Pad

This paper presents a sensor-based stability walk for bipedal robots by using force sensitive resistor (FSR) sensor. To perform walk stability on uneven terrain conditions, FSR sensor is used as feedbacks to evaluate the stability of bipedal robot instead of the center of pressure (CoP). In this work, CoP that was generated from four FSR sensors placed on each foot-pad is used to evaluate the walking stability. The robot CoP position provided an indication of walk stability. The CoP position information was further evaluated with a fuzzy logic controller (FLC) to generate appropriate offset angles to be applied to meet a stable situation. Moreover, in this paper designed a FLC through CoP region's stability and stable compliance control are introduced. Finally, the performances of the proposed methods were verified with 18-degrees of freedom (DOF) kid-size bipedal robot.<br /><br />

scholarly journals A Moving 3D Laser Scanner for Automated Underbridge Inspection

2017 ◽  
Author(s):  
Marco Tarabini ◽  
Hermes Giberti ◽  
Silvio Giancola ◽  
Matteo Sgrenzaroli ◽  
Remo Sala ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Numerical Simulations ◽  
Relative Motion ◽  
Reference System ◽  
Complete System ◽  
Laser Scanner ◽  
Bridge Model ◽  
Fixed Reference ◽  
Scanning Head

Recent researches proved that the underbridge geometry can be reconstructed by mounting a 3D laser scanner on a motorized cart travelling on a walkway located under the bridge. The walkway is moved by a truck and the accuracy of the bridge model depends on the accuracy of the trajectory of the scanning head with respect to a fixed reference system. In this paper, we describe the metrological characterization of a method that uses non-contact systems to identify the relative motion of the cart with respect to the walkway; the orientation of the walkway with respect to the bridge is determined using inclinometers and optical rails, while the position of the truck with respect to the bridge is measured using a conventional odometer.&nbsp; The measurement uncertainty of the proposed system was initially evaluated by numerical simulations and successively verified by experiments in laboratory conditions. The complete system has then been tested in operative conditions; the validity of the proposed approach has been demonstrated by comparing the geometry of buildings reconstructed with the proposed system with the geometry obtained with a static scan. Results evidenced that the errors are approximately 6 mm.

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