Abstract
This chapter deals with hexapod walking robot design and operation. The first section gives a wide overview of the state-of-the-art on hexapod walking robots by referring both to early design solutions and to most recent achievements. Section two identifies the main design challenges that influence the technical feasibility and performance of these systems. In section three, a design procedure is proposed. In particular, the proposed design procedure takes into account mechanical structure, leg configuration, actuating and drive mechanisms, payload, motion conditions, walking gait, and control system. A case of study is carefully described as referring to previous experiences at LARM.
TopIntroduction
Historical evidence of legged mechanisms dates back to antiquity, such as reported in (Zielinska, 04). The long history associated with the evolution of walking machines was outlined for example in (Silva and Tenreiro Machado, 2007). Early walking machines were focused on more and more complex linkage design, driven by only one source of power. The pure mechanical solution was limited and it becomes an evidence that less predictable environment requires advanced control. Walking machine researches gathered a new momentum after the Second World War due to the new findings in mechanics, electronics and control system (Nonami et al., 2014). A number of research groups started to study and build walking machines in a systematic approach from the mid-1950s. It took another decade to have early progress in robotics as an interdisciplinary area of engineering sciences. At early of 70ies the word “mechatronics” was coined. Nowadays mechatronics is a multidisciplinary field of engineering that represents a unifying and intelligent engineering science paradigm. Mechatronics fuses and comprehends modern engineering science and technologies to enhance machine intelligence and interactions as described for example in (Habib, 2007). Advances in the fields of robotics and mechatronics made possible the development of so-called Hexapod Walking Robots (HWR). In recent years, biological approach is bringing new perspective and is giving great potential to HWR design. Biomimetics is in fact an emerging discipline that studies and examines nature, its models, processes, structures, to take inspiration from, or emulate, nature's best biological ideas in order to solve scientific and engineering problems (Habib, 2011).
The first section of this chapter begins addressing a definition of HWR. Then an historical overview is given by referring to the milestones in the history of hexapod walking robotics developments. Section two describes the design challenges that influence the technical feasibility and performance of HWR. Discussion takes into account mechanical structure, leg configuration, actuating and drive mechanisms, payload, motion conditions, walking gait, control system. A case of study is described as referring to previous experiences at LARM in Cassino, Italy.
Key Terms in this Chapter
Type Synthesis: A stage of the design process that consists in the selection of the type of leg mechanism and body architecture that is needed to accomplish a given purpose. Type synthesis is strongly related to the operation features, key features and design characteristics of a robot.
Design Issue: A design issue often represents a challenging problem through the operational requirements and capabilities of a robotic system. A design issue is usually a very important item of the design process that will lead to specific design solutions.
Preliminary Layout Design: A design procedure that assists a designer for selecting the main design characteristics and preliminary architecture of a robot. It requires as inputs the desired key features of a robot and their significance as related with the main design solutions.
Gait: A gait is as a coordinated sequence of leg motions that is needed for achieving a desired body motion for a legged robot from one place to another. Many aspects affect the choice of a proper gait including the desired motion speed and the environment conditions.
Hexapod Walking Robot (HWR): A mobile platform on which six legs are attached to the robot body. Legs are controlled with a degree of autonomy that allows a HWR robot to move within its environment for performing intended tasks.
Design Refinements: A stage of the design process that is aimed to improve the results of the preliminary layout design for identifying the final architecture of a robot. The design refinements may require kinematic models, dynamic models and optimal design procedures.
Size Synthesis: A stage of the design process that consists in the selection of the sizes of the leg mechanism and body architecture. Size synthesis is an iterative process that involves Kinematics, Dynamics often in combination with optimal design procedures.
Design Constraints: A design constraint refers to a limitation on the requirements and/or operation conditions under which a robot is expected to operate. A design constraint can, for example, affect the robot shape, the robot operation features, and the robot functionality. A design constraint can be also related to other aspects such as the manufacturing technology or the available budget for the construction of a robot.