The Cost of Transport (cot) of a High Energy Efficiency Hybrid Robot

Purpose: The cost of transport is one of the most important values to the efficiency and operation autonomy of a walking robot. This analysis involves factors as the weight, consumption of the actuators, speeds, accelerations, work surfaces, step cycle model or distance travelled, which must be studied in detail to produce stable and energy-efficient locomotion. This paper presents the results obtained for the cost of transport of a hybrid robot with two front legs and two rear wheels, with a total weight of 50 kg in different scenarios. Methodology/approach - The transportation cost of the proposed hybrid robot is obtained by carrying out a detailed analysis of the kinematics, dynamics, stability and energy consumption. Findings - A satisfactory value of efficiency has been obtained, in terms of cost of transport, owing to a gravitationally decoupled design of the legs. The cost of transport of the robot proposed is between 0.11 and 0.24, depending on the work environment in which it operates, that is, walking on a smooth horizontal plane without additional load. Originality/value – This work presents a new design of a gravitationally decoupled robotic leg by means of a new scheme in which the leg is composed of three four-bar mechanisms that can be synthesized independently. These three mechanisms involve frontal and vertical movement within the same plane of movement. One mechanism generates a horizontal path for tow, while another generates a vertical path and a third has the specific mission of making the tow velocity constant when the corresponding motor is operated at a constant velocity. The overall goal of the mechanisms is to improve robot's efficiency. Key Words: Cost of transport, gravitationally uncoupled motion, energy efficiency, experimental validation, hybrid robot.