Walking Motion Trajectory of Hip Powered Orthotic Device Using Quintic Polynomial Equation

In lower limb exoskeleton system walking motion profile generation, cubic polynomial is commonly used to generate smooth walking profile on flexion angle, velocity and acceleration data of three joint movements (ankle, knee and hip joints). However, cubic polynomial does not closely matched human motion. For this reason, a higher-order-polynomial i.e. quintic polynomial is proposed to gene- rate walking motion profile. Error analysis was conducted to measure how closely quintic polynomial could represent human walking motion profile. Result shows that quantic polynomial could closely represent human walking trajectory with maximum RMS error of 0.2607rad occurred during mid-swing phase

High accuracy walking motion trajectory generation profile based on 6-5-6-PSPB polynomial segment with polynomial blend

Many robots, such as humanoid robot, biped robot, and robotic exoskeleton, need human guide. Particularly, there is a strong need for devices to assist individuals who lost limb function due to illnesses or injuries. Thus, several methods of generating walking motion have been implemented in order to generate walking motion according to natural human behaviour for the exoskeleton robot system. Polynomial blend technique has implemented to generate the walking motion trajectory, where the polynomial blend refers to the combination of more than one polynomial. However, three constraints (angular position, velocity, and acceleration) have been imposed by the polynomial blend techniques where the constraint of angular jerk was neglected because involving the jerk constrain will be caused problem of the non-ideal match of kinematic constraints at via point. Based on the aforementioned problem, there are three objectives to be achieved in this project. The first objective is to investigate the trajectory profile for various kinematic constraints of walking motion condition when using polynomial equation. The second objective is to modify a technique for improving a trajectory generation method to solve the problem of non-ideal match of the kinematic constraints through via points that connects between successive segments of the human walking motion. The last objective is to validate the trajectory generation method by testing the trajectory generation methods based on simulation using SimMechanics as well as to ensure that the coefficients values of the polynomial equations are correctly obtained. In this project, 5th polynomial segment with the 6th polynomial blend (6-5-6 PSPB) trajectory is proposed that aims to reduce the error that increases because of non-ideal match between kinematic constraints at the via points of successive segments. The trajectory planning of the 6-5-6 PSPB is generated based on the stance and swing phases. Each phase is presented by one full of the 6-5-6 PSPB trajectory. In order to validate the 6-5-6 PSPB trajectory, simulation using SimMechanics is conducted to ensure that the coefficients values of the polynomial equations are correctly obtained. The result shows that the error was improved almost 0.1445 degree based on the proposed 6-5-6 PSPB compared with the 4-3-4 PSPB and 5-4-5 PSPB. Thus, the 6th -5th -6th Polynomial blend leads to impose the angular jerk kinematic constraint beside the angular position, velocity, and acceleration kinematic constraints during the whole walking motion trajectory. Minimizing the maximum jerk in joint space has a beneficial effect in terms of reducing the actuator and mechanical strain and joint wear and to limit excessive wear on the robot and the excitation of resonances so that the robot life-span is expanded

Walking Pattern and Compensatory Body Motion of Biped Humanoid Robot

This paper presents a walking pattern generation method for biped walking. There are three walking phases such as a double support, a swing and a contact phase. In the swing phase, a leg motion pattern is produced by using a six order polynomial, while a leg motion pattern is generated by using a quintic polynomial in the contact and double support phase. When a biped humanoid robot dynamically walks on the ground, moments are produced by the motion of the lower-limbs. So, a moment compensation method is also discussed in this paper. Based on the motion of the lower-limbs and ZMP (Zero Moment Point), the motion of the trunk and the waist is calculated to cancel the moments. Through simulation, the effectiveness of the moment compensation methods is verified

Torque Curve Optimization of Ankle Push-Off in Walking Bipedal Robots Using Genetic Algorithm

From MDPI via Jisc Publications RouterHistory: accepted 2021-05-11, pub-electronic 2021-05-14Publication status: PublishedFunder: the project of National Key R&D Program of China; Grant(s): 2018YFC2001300, 51675222Funder: National Natural Science Foundation of China; Grant(s): 91848204, 91948302Ankle push-off occurs when muscle–tendon units about the ankle joint generate a burst of positive power at the end of stance phase in human walking. Ankle push-off mainly contributes to both leg swing and center of mass (CoM) acceleration. Humans use the amount of ankle push-off to induce speed changes. Thus, this study focuses on determining the faster walking speed and the lowest energy efficiency of biped robots by using ankle push-off. The real-time-space trajectory method is used to provide reference positions for the hip and knee joints. The torque curve during ankle push-off, composed of three quintic polynomial curves, is applied to the ankle joint. With the walking distance and the mechanical cost of transport (MCOT) as the optimization goals, the genetic algorithm (GA) is used to obtain the optimal torque curve during ankle push-off. The results show that the biped robot achieved a maximum speed of 1.3 m/s, and the ankle push-off occurs at 41.27−48.34% of the gait cycle. The MCOT of the bipedal robot corresponding to the high economy gait is 0.70, and the walking speed is 0.54 m/s. This study may further prompt the design of the ankle joint and identify the important implications of ankle push-off for biped robots

A Hybrid Planning and Control Model for Biped Feet Rotation

This thesis proposes methods for biped walking locomotion with feet rotation. The chief objective of this work is to first generate a guide trajectory based on designing a zero moment point (ZMP) trajectory within the support polygon and obtain linear controlling methods to stabilize the walking procedure with feet rotation. With feet rotation, the walking procedure will be more humanlike, more flexible and possible saving energy. However, when the feet are rotating around their edge, either toe or heel, the entire robot is under-actuated which are more difficult to control. By using preview control, a dynamic model of the system can be derived to control the robot. This thesis is based upon a simplified model of the Reemc Robot by PAL Robotics. The simplified model has fixed arms, since only leg motions are considered, and two legs. Each leg has three degrees of freedom. The robot is presented as a three mass model. A guided gait trajectory is first generated as the boundary condition for the ZMP. Interpolation methods are used to generate a ZMP trajectory from a set of discrete points that stay inside the boundary condition. By designing the transition model from single support phase and double support phase, a general schema can be achieved. Following the assumptions of a linear inverted pendulum, trajectories of all three masses can be solved. Inverse kinematics can now give the reference joint trajectories, which, together with the reference ZMP trajectory, is used in control methods to minimize the error between the reference trajectory and actual trajectory in simulation. Control methods are used to stabilize the motion of the walking procedure. Preview control is used for the single support phase where the behavior of all three masses is linear. A proper input can be obtained through optimization. During the double support phase, the feet rotations are nonlinear and under-actuated since the feet are rotating around their edge where no torque can be produced from the ground. By using preview control, an input can be applied to the robot so that the robot can maintain dynamic stability.Ope

Optimisation of bipedal walking motion with unbalanced masses.

Commercial prosthetic feet weigh about 25% of their equivalent physiological counterparts. The human body has a tendency to overcome the walking asymmetry resulting from the mass imbalance by exerting more energy. A two link passive walking kinematic model, with realistic masses for prosthetic, physiological legs and upper body, has been proposed to study the gait pattern with unbalanced leg masses. The 'heel to toe' rolling contact has significant influence on the dynamics of biped models. This contact is modelled using the roll-over shape defined in the local co-ordinate system aligned with the stance leg. The effect of rollover shape curvature and arc length has been studied on various gait descriptors such as average velocity, step period, inter leg angle (and hence step length), mechanical energy. The bifurcation diagrams have been plotted for point feet and different gain values. The insight gained by studying the bifurcation diagrams for different gain and length values is not only useful in understanding the stability of the biped walking process but also in the design of prosthetic feet. It is proposed that the stiffness and energy release mechanisms of prosthetic feet be designed to satisfy amputee's natural gait characteristics that are defined by an effective roll-over shape and corresponding ground reaction force combinations. Each point on the roll-over shape is mapped with a ground reaction force corresponding to its time step. The resulting discrete set of ground reaction force components are applied to the prosthetic foot sole and its stiffness profile is optimised to produce a desired deflection as given by the corresponding point on the roll-over shape. It is shown that the proposed methodology is able to provide valuable insights in the guidelines for selection of materials for a multi-material prosthetic foot

Arbitrary trajectory foot planner for bipedal walking

© 2017 by SCITEPRESS - Science and Technology Publications, Lda. All Rights Reserved. This paper presents a foot planner algorithm for bipedal walking along an arbitrary curve. It takes a parametrically defined desired path as an input and calculates feet positions and orientations at each step. Number of steps that are required to complete the path depends on a maximum step length and maximum foot rotation angle at each step. Provided with results of the foot planner, our walking engine successfully performs robot locomotion. Verification tests were executed with AR601M humanoid robot

Learning Motion Skills for a Humanoid Robot

This thesis investigates the learning of motion skills for humanoid robots. As groundwork, a humanoid robot with integrated fall management was developed as an experimental platform. Then, two different approaches for creating motion skills were investigated. First, one that is based on Cartesian quintic splines with optimized parameters. Second, a reinforcement learning-based approach that utilizes the first approach as a reference motion to guide the learning. Both approaches were tested on the developed robot and on further simulated robots to show their generalization. A special focus was set on the locomotion skill, but a standing-up and kick skill are also discussed. Diese Dissertation beschäftigt sich mit dem Lernen von Bewegungsfähigkeiten für humanoide Roboter. Als Grundlage wurde zunächst ein humanoider Roboter mit integriertem Fall Management entwickelt, welcher als Experimentalplatform dient. Dann wurden zwei verschiedene Ansätze für die Erstellung von Bewegungsfähigkeiten untersucht. Zu erst einer der kartesische quintische Splines mit optimierten Parametern nutzt. Danach wurde ein Ansatz basierend auf bestärkendem Lernen untersucht, welcher den ersten Ansatz als Referenzbewegung benutzt. Beide Ansätze wurden sowohl auf der entwickelten Roboterplatform, als auch auf weiteren simulierten Robotern getestet um die Generalisierbarkeit zu zeigen. Ein besonderer Fokus wurde auf die Fähigkeit des Gehens gelegt, aber auch Aufsteh- und Schussfähigkeiten werden diskutiert