DYNAMIC CONTROL ALGORITHM FOR A BIPED ROBOT

In this paper, a high-level real-time control strategy for a bipedal walking robot is presented. The considered motion is a steady walking pattern with instantaneous double support phase. The presented algorithm introduces a number of objective locomotion parameters which char- acterize the steps, and at the same time controls the upper body motion. Polynomial trajectories are designed to be tracked by the different controllers of the leg links. These trajectories deal with the fact that the ankle torque is limited by the physical length of the foot. The motion of the upper body is quasi naturally steered by using the angular momentum equation in a convenient way. Only a small ankle torque has to be added to reach exactly the desired conditions for the upper body. Promising results of the simulations are shown.

In this article, we intend to consider the behavior and control of a biped walking robot using kinematic and dynamic relations. At first, by using simple model of humanoid robot and essentional equations the angles, angular velocities, accelerations of motors and required torques for moving on a straight line are find out. In the second step considering numerical values of the robot parameters and constructing the dynamic model the abilities of robot are examined and simulated.

1999

We want to control an anthropomorphic biped robot to make it walk in its environment. For this purpose, we need complete walk trajectories. We start with cyclic trajectories obtained with motion capture on a human. Then, we want to generate transient trajectories with a fast and on-line method, in order to complete cyclic trajectories provided by motion capture. We thus use a method based on cubic polynomials. We apply this method on a human walk trajectory, to compute start and stop transient trajectories for the robot.

Robotica, 1999

This paper addresses the problem of modeling biped dynamics and the use of such models for the control of walking, running and jumping robots. We describe two approaches to dynamic modeling: the basic Lagrange approach and the non-regular dynamic approach. The new non-regular dynamic approach takes into account discontinuities due to rigid contact between punctual feet and the ground without computing the exact impact time. The contact is close to the physical situation given by non-linear laws (impenetrability, non-smooth contact and real friction cone). Contact dynamics can be well managed with an accurate dynamic model that respects energy consistency during all the phases encountered during a step (0, 1 or 2 contacts). With this model, we can first study the equilibrum of a biped standing on one foot by a linearisation method. In the second stage, the unified modelized equation is used to establish a general control frame based on non-regular dynamical decoupling. A comparison i...

2001

A 3-dimensional computer model of sustainedbipedal walking is presented. It is intended be used as adevelopment tool for walking controllers. The directdynamic simulation has 8 segments, 19 degrees offreedom and is driven by prescribed joint moment andstiffness trajectories. Limited feedback in the form of aproportional-derivative controller provides upper bodystability and allows walking to be sustained indefinitely.The joint moment and stiffness trajectories are specifiedin coarse block segments. By changing the intensity of hipextensor activity during terminal stance the walking stridelength is modulated.

Robotica, 2013

In order to obtain a more human-like walking and less energy consumption, a foot rotation phase is considered in the single support phase of a 3D biped robot, in which the stance heel lifts from the ground and the stance foot rotates about the toe. Since there is no actuation at the toe, a walking phase of the robot is composed of a fully actuated phase and an under-actuated phase. The objective of this paper is to present an asymptotically stable walking controller that integrates these two phases. To get around the under-actuation issue, a strict monotonic parameter of the robot is used to describe the reference trajectory instead of using the time parameter. The overall control law consists of a zero moment point (ZMP) controller, a swing ankle rotation controller and a partial joint angles controller. The ZMP controller guarantees that the ZMP follows the desired ZMP. The swing ankle rotation controller assures a flat-foot impact at the end of the swinging phase. Each of these controllers creates two constraints on joint accelerations. In order to determine all the desired joint accelerations from the control law, a partial joint angles controller is implemented. A word "partial" emphasizes the fact that not all the joint angles can be controlled. The outputs controlled by a partial joint angles controller are defined as a linear combination of all the joint angles. The most important question addressed in this paper is how this linear combination can be defined in order to ensure walking stability. The stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincaré map of the hybrid zero dynamics. Finally, simulation results validate the effectiveness of the control law even in presence of initial errors and modelling errors.

International Journal of Computer Applications, 2014

This paper proposes a thorough algorithm that can tune the walking parameters (hip height, distance traveled by the hip, and times of single support phase SSP and double support phase DSP) to satisfy the kinematic and dynamic constraints: singularity condition at the knee joint, zero-moment point (ZMP) constraint, and unilateral contact constraints. Two walking patterns of biped locomotion have been investigated using the proposed algorithm. The distinction of these walking patterns is that the stance foot will stay fixed during the first sub-phase of the DSP for pattern 1, while it will rotate simultaneously at beginning of the DSP for pattern 2. A seven-link biped robot is simulated with the proposed algorithm. The results show that the proposed algorithm can compensate for the deviation of the ZMP trajectory due to approximate model of the pendulum model; thus balanced motion could be generated. In addition, it is shown that keeping the stance foot fixed during the first sub-phase of the DSP is necessary to evade deviation of ZMP from its desired trajectory resulting in unbalanced motion; thus, walking pattern 1 is preferred practically.

—This work aims to design an optimal dynamic controller to stabilize the walk of a biped robot even in the presence of input and output constraints. In a first time, the robot's trajectory is generated via the Zero Moment Point criterion based on the resolution of a convex optimization problem with Linear Matrix Inequalities. In a second time, the tracking of a reference trajectory is insured by the design of an optimal dynamic controller based on the predictive control theory. The synthesized dynamic controller allows for the Lyapunov stability of the robot's walk. Moreover, it ensures the reducing of the overshoot and undershoot of the output signal that are difficult to be adjusted by classical methods based on solving the algebraic Riccati equation. This study is validated by a simulation via Matlab of some illustrative examples. Results are presented to prove the effectiveness of the proposed work.

This paper proposes a robust mathematical approach for motion control. The proposed control tech-nique is applied to a three-degree of freedom Biped walking robot for illustration. The design technique is di-vided into two major steps; the first one is to establish a robust position control scheme with both guaranteed stability and trajectory tracking capability using a model-reference technique that assumes only the knowledge of the upper bound of the model uncertainty. The performance of this step is investigated for the two cases of point-to-point and trajectory-following motions. The second step is to design an intelligent path planner for the walking Biped that takes all motion constraints into account. Animation is used to check for both motion har-mony and trajectory following. The real-time applicability of the proposed controller is investigated and tra-deoffs between stability and performance are carefully studied. In addition, real-time potential of the controller is bein...

Strojnícky casopis – Journal of Mechanical Engineering, 2018

This paper focuses on the walking improvement of a biped robot. The zero-moment point (ZMP) method is used to stabilise the walking process of robot. The kinematic model of the humanoid robot is based on Denavit- Hartenberg’s (D-H) method, as presented in this paper. This work deals with the stability analysis of a two-legged robot during double and single foot walking. It seems more difficult to analyse the dynamic behaviour of a walking robot due to its mathematical complexity. In this context most humanoid robots are based on the control model. This method needs to design not only a model of the robot itself but also the surrounding environment. In this paper, a kinematic simulation of the robotic system is performed in MATLAB. Driving torque of the left and right ankle is calculated based on the trajectory of joint angle, the same as angular velocity and angular acceleration. During this process an elmo motion controller is used for all joints. The validity of the dynamic model ...

IFAC Proceedings Volumes, 2013

Analytical techniques are presented for the motion planning and control of a 10 degree-of-freedom biped walking robot. From the Denavit-Hartenberg method and Newton-Euler equations, joint torques are obtained in terms of joint trajectories and the inverse dynamics are developed for both the single-support and double-support cases. Physical admissibility of the biped trajectory is characterized in terms of the equivalent force-moment and zero-moment point. This methodology has been used to obtain stability of walking biped robot Archie developed in IHRT. A simulation example illustrates the application of the techniques to plan the forward-walking trajectory of the biped robot.

IEEE/ASME Transactions on Mechatronics, 2000

This paper proposes a 3-D biped dynamic walking algorithm based on passive dynamic autonomous control (PDAC). The robot dynamics is modeled as an autonomous system of a 3-D inverted pendulum by applying the PDAC concept that is based on the assumption of point contact of the robot foot and the virtual constraint as to robot joints. Due to autonomy, there are two conservative quantities named "PDAC constant," which determine the velocity and direction of the biped walking. We also propose the convergence algorithm to make PDAC constants converge to arbitrary values, so that walking velocity and direction are controllable. Finally, experimental results validate the performance and the energy efficiency of the proposed algorithm.

2004

We present a new method for generating controllers for physics-based simulations of planar bipedal walking, targeted towards producing autonomous character behaviors for computer animation. A common criticism of physics-based character animation is the lack of personality and style in the final motion. We develop controllers that mimic a desired style as much as possible, while still subject to the laws of physics and to the realities of maintaining balance. The resulting simulated character can interact with and respond to its environment, unlike the original kinematically-specified desired motion. Walking is a very challenging control task because of its dynamically unstable nature. Continuous balance control is required to prevent the character from falling over or reaching poses from which it cannot recover. The complexity of a walking controller is compounded by high dimensional continuous.state and action spaces. Our controller implements a nearest-neighbor control policy with...

2010

This paper deals with design and implementation of a control architecture for 3D dynamic walking with foot/ground compliant contact. This architecture includes a ZMP-based pattern generator, a computed torque controller based on the reduced order dynamics of the system, and a stabilizer to enhance the stability robustness of the control architecture. The effectiveness of the proposed control architecture is shown through numerical simulations.