Research Topics

Online generation of high-speed foot trajectories  

Walking machines have been investigated during the last forty years and some basic techniques of this field are already well known. However, some aspects still need to be optimized. For instance, speed seems to be one of the major shortcomings of legged robots; thus, improving leg speed has been chosen as the main aim of this work. Although some algorithms for optimizing trajectory control of robot manipulators already exist, we propose a more computationally efficient method that employs fuzzy set theory to involve real dynamic effects over leg motion instead of an inaccurate mathematical model. In this work, we improve leg speed by automatically tuning the acceleration of legs. For this purpose, we define fuzzy rules based on experiments and we find the optimal acceleration for every given trajectory. A simple fuzzy inference system is used to compute the required acceleration. It is based on five rules using three linguistic variables. Final results show that foot acceleration tuning for straight trajectory generation is a suitable method for achieving accurate, smooth and fast foot movements. Also it is shown that under some conditions average leg speed can be increased up to 100 percent using the control methods herein proposed. More...

Stability of Walking Robots                                      

Several static and dynamic stability criteria have been defined in the course of walking robot history. Nevertheless, different applications may require different stability criteria and, up to day, there is no qualitative classification of such stability measurements. Using the wrong stability criterion to control a robot gait may prevent the task from succeeding. Furthermore, if the optimum criterion is found, the robot gait can also be optimised. In this work,  the stability criteria that have been applied to walking robots with at least four legs are examined in terms of their stability margins in different static and dynamic situations. As a result, a qualitative classification of stability criteria for walking machines is proposed so that the proper criterion can be chosen for every desired application. More...

Gait Adaptation to Environmental Disturbances        

Natural environments and intrinsic robot dynamics can produce instability in walking-robot gaits. In such cases, the gait should be modified to enhance the robot’s stability. This work proposes a novel gait-adaptation method based on the maximization of a dynamic energy stability margin. This method enables walking-machine gaits to adapt to internal and environmental perturbations as well as to the slope of the terrain by finding the gait parameters that maximize robot stability. The adaptation method also gives mathematical insight into the natural gait adaptation carried out by humans and animals to balance external forces or the effect of sloping terrain. Experiments with the SILO4 robot are presented that show how robot stability is enhanced when the proposed approach is used for different external forces and sloping terrains. More...

 

Active Compliance in Walking Robots                         

Robot Navigation With Complete Coverage of Unstructured Environments 

Path-planning algorithms are well understood for a variety of exploratory applications. Artificial-intelligence methods like learning algorithms are widely used to solve the problem of robot navigation in unstructured environments. However there are some types of mobile-robot applications that need a different path-planning technique. Scanning applications, like landmine detection, cleaning tasks and terrain-map generation, require not finding the shortest path to a point in the environment but scanning over all points in the environment and avoiding obstacles of unknown location. This is known as the complete-coverage problem in unstructured environments.  Our goal is to achieve complete coverage of unstructured environments for landmine detection purposes. DYLEMA project is about considering walking robots as locomotion system that carry a scanning system to detect and locate buried mines. Therefore we need to achieve complete coverage in the navigation of both walking robot and scanning system. More...

 

New Actuators for Field and Service Robots