Real-time estimation algorithm for the center of mass of a bipedal robot with flexible inverted pendulum model (original) (raw)
Center of Mass States and Disturbance Estimation for a Walking Biped
IEEE International Conference on Mechatronics, ICM 2013, , 2013
An on-line assessment of the balance of the robot requires information of the state variables of the robot dynamics and measurement data about the environmental interaction forces. However, modeling errors, external forces and hard to measure states pose difficulties to the control systems. This paper presents a method of using the motion information to estimate the center of mass (CoM) states and the disturbance of walking humanoid robot. The motion is acquired from the inertial measurement unit (IMU) and forward kinematics only. Kalman filter and disturbance observer are employed, Kalman filter is used for the states and disturbance estimation, and the disturbance observer is used to decompose the disturbance into modeling error and acceleration error based on the frequency band. The disturbance is modeled mathematically in terms of previous CoM and Zero moment point (ZMP) states rather than augmenting it in the system states. The ZMP is estimated using the quadratic programming method to solve the constraint dynamic equations of the humanoid robot in translational motion. A biped robot model of 12-degrees-of-freedom (DOF) is used in the full-dynamics 3-D simulations for the estimation validation. The results indicate that the presented estimation method is successful and promising.
Online Center of Mass Estimation for a Humanoid Wheeled Inverted Pendulum Robot
ArXiv, 2018
We present a novel application of robust control and online learning for the balancing of a n Degree of Freedom (DoF), Wheeled Inverted Pendulum (WIP) humanoid robot. Our technique condenses the inaccuracies of a mass model into a Center of Mass (CoM) error, balances despite this error, and uses online learning to update the mass model for a better CoM estimate. Using a simulated model of our robot, we meta-learn a set of excitory joint poses that makes our gradient descent algorithm quickly converge to an accurate (CoM) estimate. This simulated pipeline executes in a fully online fashion, using active disturbance rejection to address the mass errors that result from a steadily evolving mass model. Experiments were performed on a 19 DoF WIP, in which we manually acquired the data for the learned set of poses and show that the mass model produced by a gradient descent produces a CoM estimate that improves overall control and efficiency. This work contributes to a greater corpus of wh...
Estimation of Absolute Orientation for a Bipedal Robot: Experimental Results
IEEE Transactions on Robotics, 2000
This paper deals with a planar biped. The aim of this paper is the estimation, during the imbalance phases of a walking cyclic gait, of its absolute orientation by only using the measurement of the actuated joint variables. The main contribution is the experimental evaluation of an original finite-time convergent-posture observer.
Biped walking stabilization based on linear inverted pendulum tracking
Intelligent Robots and …
A novel framework of biped walking stabilization control is introduced. The target robot is a 42 DOF humanoid robot HRP-4C which has a body dimensions close to the average Japanese female. We develop a body posture controller and foot force controllers on the joint position servo of the robot. By applying this posture/force control, we can regard the robot system as a simple linear inverted pendulum with ZMP delay. After a preliminary experiment to confirm the linear dynamics, we design a tracking controller for walking stabilization. It is evaluated in the experiments of HRP-4C walking and turning on a lab floor. The robot can also perform an outdoor walk on an uneven pavement.
Considerations on Dynamic and Static Stability of a Biped Robot
This paper describes the control of a biped robot, that uses an inverted pendulum for its balance. A control method that consists of the balance of the gaits, through the correction of the lateral and longitudinal angles of the pendulum is proposed in this work. This method p resents three phases: first t he trajectory of the foot i n movement is defined, applying the inverse kinematics to calculate the robot's internal angles, and the direct kinematics is used to ob tain the positions and o rientations of the robot's joints; then the linear and angular accelerations are obtained; l ast, the zero moment point (ZMP) is calculated as a verification parameter of the requested margin of stability. Simulation of the robot gaits to walk in horizontal, sloping plans, and up and down stairs is also made. In order to decrease the calculation time of the dynamic stability, the impact of using zero pendulum angles as starting points for the interactive process of achieving the desire...
An inverted pendulum based approach to biped trajectory generation with swing leg dynamics
2007 7th IEEE-RAS International Conference on Humanoid Robots, 2007
Reference trajectory generation is one of the key problems in biped walking robot research. The linear inverted pendulum model (LIPM) is employed widely as a useful model which simplifies trajectory generation task. Many reference generation algorithms use the Zero Moment Point (ZMP) Criterion for the LIPM in order to achieve stable walking trajectories. However, LIMP ignores the dynamics of the swing leg. This can lead to tracking problems, especially when the legs are heavy. This paper uses a two-mass LIPM and proposes a fifth order state space description for the dynamics of the robot body and the swing leg in the swing phase. The body center of mass (CMB) reference trajectory is obtained for given foot placement references and the desired ZMP trajectory. An inverse kinematics based position controller is then employed for locomotion. The walking performances with the one-mass and one-mass-two-mass switching linear inverted pendulum models are finally compared via 3D full-dynamics simulations of a 12 degrees of freedom (DOF) biped robot. The results indicate that the proposed model switching between one-mass and two-mass models is useful in improving the stability of the walk.
A Walking Bipedal Robot Using a Position Control Algorithm Based on Center of Mass Criterion
2019
A position control algorithm based on inverse kinematics and a control strategy utilizing the Center of Mass criterion are implemented to yield a walking bipedal robot. The bipedal robot has no upper body, stands approximately 50 cm and weighs about four kg. Each leg of the robot has five degrees of freedom: two at the hip, two at the ankles, and one at the knee. The closed form solution of each joint angle is derived by using inverse kinematics, following the DenavitHartenberg guidelines to determine the structural parameters of the biped. Such closed form equations determine the value of the joint angle to achieve an instance needed to complete the walking activity. Bipedal locomotion is verified by both simulation and experiments. Simulation results provide desired joint angle trajectories and will serve as benchmark for the actual experiments. Experimental results show that actual step length, foot clearance and hip height gait parameters do not exceed one centimeter from the ta...
A method for the calculation of the effective Center of Mass of humanoid robots
2011
In this paper we present a general strategy for the calculation of the effective Center of Mass (CoM) of humanoid robots, allowing the reduction of the error between the virtual robot model and the real platform. The method is based on an algorithm that calculates the real position of the CoM of a biped humanoid robot using only 2 force/torque sensors located on the feet of the robot. By means of this algorithm, it is possible to reduce the gap between the real and the virtual posture of the robot and consequently the errors between the ZMP trajectory calculated by the offline pattern generator and the ZMP trajectory calculated by the real-time pattern generator of the humanoid robot. Thus, the influence of the real-time control in the static and dynamic balance of a humanoid platform is minimized. Experimental results using SABIAN platform are provided to validate the proposed method. The results support the applicability of the method to more complex systems.
Calculation of the Center of Mass Position of Each Link of Multibody Biped Robots
Applied Sciences
In this paper, a novel method to determine the center of mass position of each link of human-like multibody biped robots is proposed. A first formulation to determine the total center of mass position has been tested in other works on a biped platform with human-like dimensions. In this paper, the formulation is optimized and extended, and it is able to give as output the center of mass positions of each link of the platform. The calculation can be applied to different types of robots. The optimized formulation is validated using a simulated biped robot in MATLAB.
Modeling and dynamic analysis of the biped robot
2015 15th International Conference on Control, Automation and Systems (ICCAS), 2015
Abstract: Biped robots have several degrees of freedom (DOF) composed of many articulated links connected together by joint which ends up in a complex structure and difficult to make it mimic human like locomotion gait which is dynamic in nature and at the same time stable in the sense of not falling by. This paper presents dynamic equations of motion and its Matlab simulation of joints position. These dynamic equations are derived by starting with the kinematics which includes forward kinematics (FK) derived by using the Denavit-Hartenberg notation and inverse kinematics (IK) and then solving the dynamics of the biped robot. Two well-known methods for solving the dynamic of the robot are Newton-Euler formulation and Euler-Lagrangian formulation. This work uses the Euler-Lagrange formulation as it is a fancy formulation technique for solving dynamics instead of finding all the forces, velocities using Newton-Euler formulation.
Sensors and Control Concept of a Biped Robot
IEEE Transactions on Industrial Electronics, 2004
The biped robot "Johnnie" is designed to achieve a dynamically stable gait pattern, allowing for high walking velocities. Very accurate and fast sensors were developed for the machine. In particular, the design of the three-dimensional-orientation sensor and the six-axes force-torque sensor are presented. The control scheme is based on the information from these sensors to deal with unstructured terrain and disturbances. Two different implementations are investigated: a computed torque approach and a trajectory control with adaptive trajectories. Walking speeds of 2.4 km/h have been achieved in experiments.
Quasi-inverse pendulum model of 12 DoF bipedal walking
International Journal of Automation and Computing, 2017
This paper presents modeling of a 12-degree of freedom (DoF) bipedal robot, focusing on the lower limbs of the system, and trajectory design for walking on straight path. Gait trajectories are designed by modeling of center of mass (CoM) trajectory and swing foot ankle trajectory based on stance foot ankle. The dynamic equations of motion of the bipedal robot are derived by considering the system as a quasi inverted pendulum (QIP) model. The direction and acceleration of CoM movement of the QIP model is determined by the position of CoM relative to the centre of pressure (CoP). To determine heel-contact and toe-off, two custom designed switches are attached with heel and toe positions of each foot. Four force sensitive resistor (FSR) sensors are also placed at the plantar surface to measure pressure that is induced on each foot while walking which leads to the calculation of CoP trajectory. The paper also describes forward kinematic (FK) and inverse kinematic (IK) investigations of the biped model where Denavit-Hartenberg (D-H) representation and Geometric-Trigonometric (G-T) formulation approach are applied. Experiments are carried out to ensure the reliability of the proposed model where the links of the bipedal system follow the best possible trajectories while walking on straight path.
International Workshop on Variable Structure Systems, 2006. VSS'06., 2006
An observer to determine the absolute orientation of a 5-link biped robot is designed, in order to avoid the use of a sensor, which is one of the originalities of this paper. As a matter of fact, the measurement of such variable is quite delicate. The observer is based on the high order sliding mode approach, for its features of robustness and finite-time convergence property.
Modeling and Kinematic Analysis of the Biped Robot
Modeling and Kinematics Analysis of the Biped Robot, 2015
Biped robots are intricate in design, with more degrees of freedom (DOF) because of the challenging goal of imitating humanoid gait. This paper gives a very simple architecture of the biped robot have three degrees of freedom (DOF)in each leg, one DOF for hip joint and one corresponding to the knee and ankle joint respectively. Denavit-Hartenberg parameter is being used to obtain the solution for forward kinematics (FK). Furthermore the forward kinematics is also confirmed using Peter-Corke toolbox in this work. This gives the desired results of the different orientation. The CAD model is also made to give a better visual model of the biped robot. Keywords—Biped robot, Design, Denavit-Hartenberg parameters, Forward kinematics
ArXiv, 2020
Although humanoid robots are made to resemble humans, their stability is not yet comparable to ours. When facing external disturbances, humans efficiently and unconsciously combine a set of strategies to regain stability. This work deals with the problem of developing a robust hybrid stabilizer system for biped robots. The Linear Inverted Pendulum (LIP) and Divergent Component of Motion (DCM) concepts are used to formulate the biped locomotion and stabilization as an analytical control framework. On top of that, a neural network with symmetric partial data augmentation learns residuals to adjust the joint's position, and thus improving the robot's stability when facing external perturbations. The performance of the proposed framework was evaluated across a set of challenging simulation scenarios. The results show a considerable improvement over the baseline in recovering from large external forces. Moreover, the produced behaviors are human-like and robust to considerably no...
2012 12th IEEE International Workshop on Advanced Motion Control (AMC), 2012
This paper proposes kinematics and a control algorithm to control a two-link manipulator to simulate a spring loaded inverted pendulum (SLIP). End-effector kinematics is derived in the reference frame that is defined along the axis that connects the first joint and the end-effector. The derivation of this kinematics reveals that a biarticular actuator is suitable for this kinematics. Based on this kinematics, a disturbance observer is designed in the same reference frame. This disturbance observer removes the unnecessary inertia coupling without calculation of Jacobian matrix.
Kinematics and dynamics modelling of the biped robot
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.
Walking principle of bipcd robot is clarified with Z M P (Zem Moment Point) concept, friction constraint, and inverted pendulum model in this paper. The stable waking condition is derived out with ZMF' constraint, friction constraint, and inverted pendulum model. With this result, the nature tbat the biped walking is in fact a continually acceleration and deceleration motion is presented and its walking velocity can be adjusted by controlling landing point. The desired ZMP trajectory is given out based on derived stable walking condition, and the motion parameters of bipcd robot, such as waking stride, period, and their restriction are investigated. The approach used in this paper is expected to exend to analyze the motion of running and jump robot.