Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> Abstract We present the biomimetic control scheme for the walking robot SCORPION. We used a concept of Basic Motion Patterns, which can be combined in a very flexible manner. Also reflexes are introduced to increase the reactivity. In addition our modeling and simulation approach is described, which has been done based on the ADAMS™ simulator. Especially the motion patterns of real scorpions were analyzed and used for walking patterns and smooth acceleration of the robot. <s> BIB001 </s> Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> In this paper, we describe experimental work using an underwater, biomimetic, eel-like robot to verify a simplified dynamic model and open-loop control routines. We compare experimental results to previous analytically derived, but approximate expressions for proposed gaits for forward/backward swimming, circular swimming, sideways swimming and turning in place. We have developed a five-link, underwater eel-like robot, focusing on modularity, reliability and rapid prototyping, to verify our theoretical predictions. Results from open-loop experiments performed with this robot in an aquatic environment using an off-line vision system for position sensing show good agreement with theory. <s> BIB002 </s> Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> We present a novel fish robot capable of swimming and crawling. The robot is driven by DC motors and has three actuated fins, with two pectoral fins and one caudal fin. It is loosely inspired from the boxfish. The control architecture of the robot is constructed around a central pattern generator (CPG) implemented as a system of coupled nonlinear oscillators, which, like its biological counterpart, can produce coordinated patterns of rhythmic activity while being modulated by simple control parameters. Using the CPG model, the robot is capable of performing and switching between a variety of different locomotor behaviors such as swimming forwards, swimming backwards, turning, rolling, moving upwards/downwards, and crawling. These behaviors are triggered and modulated by sensory input provided by light and water sensors. Results are presented demonstrating the agility of the robot, and interesting properties of a CPG-based control approach such as stability of the rhythmic patterns due to limit cycle behavior, and the production of smooth trajectories despite abrupt changes of control parameters <s> BIB003 </s> Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> In this study, we examine, for a six-link snake robot, how an optimal gait might change as a function of the snake- surface interaction model and how the overall locomotion performance changes under nonoptimal conditions such as joint failure. Simulations are evaluated for three different types of friction models, and it is shown that the gait parameters for serpentine motion are very dependant on the frictional model if minimum power expenditure is desired for a given velocity. Experimental investigations then motivate a surface interaction model not commonly used in snake locomotion studies. Using this new model, simulation results are compared to experiments for nominal and nonnominal locomotion cases including actuator faults. It is shown that this model quite accurately predicts locomotion velocities and link profiles, but that the accuracy of these predictions degrades severely at speeds where actuator dynamics become significant. <s> BIB004 </s> Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> Biological systems seem to have a simpler but more robust locomotion strategy than that of the existing biped walking controllers for humanoid robots. We show that a humanoid robot can step and walk using simple sinusoidal desired joint trajectories with their phase adjusted by a coupled oscillator model. We use the center-of-pressure location and velocity to detect the phase of the lateral robot dynamics. This phase information is used to modulate the desired joint trajectories. We do not explicitly use dynamical parameters of the humanoid robot. We hypothesize that a similar mechanism may exist in biological systems. We applied the proposed biologically inspired control strategy to our newly developed human-sized humanoid robot computational brain (CB) and a small size humanoid robot, enabling them to generate successful stepping and walking patterns. <s> BIB005 </s> Intelligent Approaches in Locomotion - A Review <s> Simple sinusoidal systems <s> Research on humanoid robotics in Mechatronics and Automation (MA) Laboratory, Electrical and Computer Engineering (ECE), National University of Singapore (NUS) was started at the beginning of this decade. Various research prototypes for humanoid robots have been designed and are going through evolution over these years. These humanoids have been successfully participating in various robotic soccer competitions. In this paper, three major research and development aspects of the above humanoid research are discussed. The paper focuses on various practical and theoretical considerations involved in processing architecture, gait generation and vision systems. <s> BIB006
These systems are based on simple sinusoidal oscillators. Coupling terms added to each oscillator equation allow phase relationships to be established between them. In BIB003 , this form of oscillator acted as the basis of a CPG controlling a swimming robot. Oscillators with amplitude and angle offsets controlled each fin. Setting different values for these two controls enabled forward swimming, backward swimming, spinning, turning while swimming, turning on the spot, swimming up or down and crawling gaits. For some systems, their locomotion comes from whole body sinusoidal movement. In order to replicate movement seen in nature, simple sinusoidal oscillators were used to produce forward, circular, turning and sideways movement in an eel robot BIB002 ,  . Sinusoidal control of serpentine motion on a planar surface was investigated in BIB004 . Of interest was the mechanical efficiency of the gait for a range of speeds, and optimisation was used to find the best values for the constants in the algorithm, under three different friction models. For other systems, such as bipeds, sinusoidal motion does not initially seem a good option. However, in BIB005 , simple sinusoidal oscillators were combined to construct gaits for two humanoid robots, one of which was human sized. The coupling of different oscillators allowed more complicated trajectory shapes, suitable for bipedal locomotion. Systems with several legs (four or more) can be stable enough to allow a leg to be moved without worrying about the system falling over. Without stability requirements, the control mechanism can be very simple. For example, simple sinusoidal oscillators were used in BIB001 to control an eight legged robot simulation. A simple oscillator system coupled with feedback, investigated in BIB006 , was able to produce faster walking speeds than a ZMP IMP approach.