Dainius Udris

Leg placement algorithm for foot impact force minimization

Walking is considered to be a rather complicated task for autonomous robots. Sustaining dynamic stability, adopting different gaits, and calculating correct foot placement are a necessity to overcome irregular terrain, various environments and completing a range of assignments. Besides that, certain assignments require that robots have to walk on fragile surfaces without damaging it. Furthermore, under some other circumstances, if walking is careless, robots could suffer damage caused by the impact of the terrain. Foot placement, leg motion speed must be controlled to avoid braking surface or even sensors on robot’s feet. In this article, a simple leg placement algorithm is proposed that controls hexapod robot’s leg speed. Thus, force dependence on leg motion speed and step height has been measured by using a piezoelectric sensor. Then, by using leg placement algorithm, we show that the reduction of the impact force between robot’s foot and surface is possible. Using this algorithm, robot feet’s impact force with the surface can be minimized to almost 0 N.

Statically stable hexapod robot body construction

Legged locomotion is becoming more and more appealing to robotic engineers. Compared to wheeled and tracked vehicles walking robots are much more effective in overcoming irregular terrain and adapting to various environments. However, walking is considered a very complex task due to the kinematics and dynamics of walking patterns, energy consumption and the necessity to sustain static and dynamic stability all the time. In this paper we propose a hexapod robot body shape to achieve maximum static stability. First, hexapod robot development is discussed including leg design and body shape. Then, using mathematical modeling software a most suitable parameters for hexapod type body are obtained and final hexapod robot model is constructed.

Hexapod robot gait stability investigation

Environmental adaptability, terrain locomotion is what makes walking robots so appealing. Due to a high number of degrees of freedom walking machines tend to be more useful in dangerous or impassible environments. Multi-legged robots have better stability while walking because there are always at least three legs supporting the robot. But having six or more legs also means that choosing or developing most suitable walking patterns is very challenging. In this paper we present a stability investigation of different hexapod robot gaits. Stability of gaits is measured by body tilt during movement. Three different gaits are used: tripod gait, wave gait, and ripple gait. Comparison of each gaits stability with various leg transfer sequences is given. Results show that the most stable gait is wave with the basic leg transfer sequence.

Piezoelectric force sensors for hexapod transportation platform

AbstractRough terrain is one of the major issues for transporting various objects to different remote locations. Wheeled platforms or robots are not suitable for such tasks due to a lack of ground clearance. Walking robots, despite their slower speed, can be successfully used as transportation platforms that can overcome the environment. However, leg placing requires accurate supervision and the force sensing system must be developed on each foot to acquire equal force distribution between legs and to obtain stable motion over the irregular surface. In this paper, we investigate the improvement of the hexapod robots feet by upgrading them with piezoelectric force sensors. By monitoring force dependence on transferred legs, we establish the most suitable hexapod gait for moving over the even surface.

Real-Time Online Feet Trajectory Generation Method for Hexapod Robot

Hexapod walking robot is a complex electromechanical system with many degrees of freedom. Six legs ensure robot’s stability as at least three legs are always on the ground but require more effort in order to synchronize them for a successful locomotion. In this paper, we present a method that allows calculate feet trajectories in real-time and online. This method enables to select different gaits and their parameters.

Minimizing Hexapod Robot Foot Deviations Using Multilayer Perceptron

Rough-terrain traversability is one of the most valuable characteristics of walking robots. Even despite their slower speeds and more complex control algorithms, walking robots have far wider usabi...

Research of Hexapod Robot Motion in Irregular Terrain

This paper presents two inverse kinematics methods for position calculation of one leg hexapod robot. Further it is explained how inverse kinematics method could be applied to calculate robot body position. A trajectory repetition precision experiment was conducted for evaluation of dependence between trajectory repetition and a number of points used to describe it.

Improvement of Precise Angle Control System

The main task of this research was improvement of precision of positioning drive, installed in a test rig for testing and calibration of the geodetic instruments at Institute of Geodesy of Vilnius Gediminas Technical University. Replacement of a stepper motor and a microstepping controller design increased positioning accuracy up to 0.1. Vibrations and noise of the test rig were significantly reduced using an optimized control algorithm, where resonating step frequencies were bypassed. Time of scale rotation between measurements (every 30) reached less than 1.5 min. Methods for further precision improvement were evaluated and this research is currently in progress.

Statistical Characteristics of a Simplex Search with the Aim Drift

The purpose of this research is to find and analyze statistical characteristics of a simplex search in a noisy surrounding and drifting aim conditions. The search process is described by using multiple Markov chains. Efficient simplex search algorithms for nonstationary object optimisation can be created on this investigation basis.