Stair-climbing is a necessary capacity for mobile robots. This paper presents an online control method for the stair-climbing of a transformable tracked robot, Amoeba-II, and this robot is also an isomerism-modules robot with different mechanism modules. Based on the reasonable compartmentalization and kinematics analysis of the stair-climbing process, the coordination of the rotations of modules can reduce the slippage between tracks and terrain. To ensure that the robot can climb stairs with enough capability and stability, the stair-climbing criterion for the robot has been established based on the force analysis of each stage of the stair-climbing procedure. Meanwhile, the interference-avoiding criterion has been set up to avoid the interference between the non-tracked module of the robot and the stair. The experiment for the stair-climbing of the robot has been implemented to certify the validity of the online stair-climbing control method for a transformable tracked robot.

This paper presents an optimal design method for a new robot called amphibious transformable robot which can not only perform reconfiguration but also implement tasks in amphibious environment. To satisfy a range of performance requirements for the robot in aquatic and terrestrial environments, the multi-objective optimization method is adopted to design the robot which can achieve the optimal comprehensive performance in the amphibious environment. Based on the kinematics and dynamic analysis of the robot, the multi-objective optimization problem of the mechanism parameters design is established on the mapping relationships between the performance indexes, and then Multi-Objective Genetic Algorithm is proposed to get Pareto solution. Based on combination weighting method of multi-attribute decision-making, the result can be extracted and used to direct the mechanism design of the amphibious transformable robot, Amoeba-II. The experiment for the maneuverability of Amoeba-II in the amphibious environment is performed to verify the validity and applicability of the mechanism-parameters design method of amphibious transformable robot based on Multi-Objective Genetic Algorithm.

Connectionist Central Pattern Generator models (CCPG) are helpful to understand how the CPG neural mechanism functions, and have relatively small complexity which makes them suitable for controlling snake-like robots. However, there are few CCPG models are constructed to generate the snake-like robot's three-dimensional gaits, which are important for adapation, and their gaits generation ability is also very inadequate. According to the CPG mechanism, a hierarchical CCPG model (HCCPG) with small complexity is proposed to implement the three-dimensional gaits better. The HCCPG has a two-layers structure, namely the basic rhythmic signal generation layer and the output signal modulation layer. The HCCPG can generate three-dimensional gaits well and is extendable. Based on the HCCPG, a three-dimensional gait control method is proposed. The simulations and experiments validate this method.

Our amphibious snake-like robot conquers the terrestrial and aquatic environments with different kinds of gait. Future work has been planned to apply the robot in inspection tasks in complicated wild environments.

Making biomimetic robots move like natural animals is an interesting problem, because this topic involves not only the low level algorithm that controls the movement of robots' bodies and limbs but also the high level control strategy that deals with different kinds of situations. Based on a certain biological assumption, a self-tuning multi-phase CPG for snake robots is proposed. This method imitates the control strategy of natural snake's movement in different environments, which enables the snake robot to move more quickly and naturally. Through kinematic and dynamic analysis of snake robots, optimal control parameters are chosen for the decision strategy. Due to the intrinsic property of the multi-phase CPG, this model can change the movement patterns and control parameters autonomously according to external information. As a result, such neural control provides a powerful but simple way to self-tune adaptable behaviors in snake robots.

This paper presents a self-rescue mechanism for a screw drive in-pipe robot, which only uses one DC motor. The robot has two working modes, Normal Working Mode and Self-rescue Mode. Under normal working mode, the robot propels itself in the pipe just as other classical screw drive robots. When the robot encounters the obstacle and gets jammed, the lock up mechanism and motion control mechanism of the robot are activated. Then, the robot changes from working mode to self-rescue mode and moves away in the reverse direction to avoid jamming in the pipe. The change of the working mode is determined by the characteristics of the mechanism. The proposed mechanism can be used as a safety protection method for the pipe robot. Experiments have been conducted to testify the proposed mechanism. Compared with those with screw drive mechanisms, robots with self-rescue mechanism are able to avoid jamming in the pipe.

The mobile robots often perform the dangerous missions such as planetary exploration, reconnaissance, anti-terrorism, rescue, and so on. So it is required that the robots should be able to move in the complex and unpredictable environment where the ground might be soft and hard, even and uneven. To access to such terrains, a novel robot (NEZA-I) with the self-adaptive mobile mechanism is proposed and developed. It consists of a control system unit and two symmetric transformable wheel-track (TWT) units. Each TWT unit is driven only by one servo motor, and can efficiently move over rough terrain by changing the locomotion mode and transforming the track configuration. It means that the mobile mechanism of NEZA-I has self-adaptability to the irregular environment. The paper proposes the design concept of NEZA-I, presents the structure and the drive system of NEZA-I, and describes the self-adaptive principle of the mobile mechanism to the rough terrains. The locomotion mode and posture of the mobile mechanism is analyzed by the means of simulation. Finally, basic experiments verify the mobility of NEZA-I.

A shape-shifting robot “AMOEBA-I” has diverse configurations, and the accessibility of the robot can be reinforced in the narrow space by changing the configurations. In this paper, a path planning method is presented corresponding to the unique reconfiguration ability of this robot. This method can automatically adjust the relation between the rapid movement and the secure mobile position of the robot based on the distribution of obstacles that are around the robot, and this method can also automatically select an appropriate configuration to adapt the robot to the environmental variation according to the information of the current conditions. The problem of deadlock is avoided by using the Boundary Following. Further, a Reconfiguration Memory is provided to optimize the trace of the Boundary Following, and it can help the robot to search a new path. Simulation results validated the advantage of the proposed method which can get the best out of the unique accessibility of the shape-shifting robot and reduced effectively the length of the robot traveling path.

The control of a snake-like robot is a challenging problem because of the complex dynamics and the unknown environment. We have proposed an energy-based method, called passive creeping, to control the serpentine locomotion. This paper lays emphasis on the stability and the adaptability of the method. First, the local orbital stability of the movement is explicated based on the maximal Lyapunov exponent and the recurrence plot. Second, the adaptability to the environment is analyzed, and an optimal adaptive law based on the energy proportion is put into use to perfect the method. The particular advantages of the passive creeping include the comprehensive concept, the explicit control, and the inherent adaptability.

This paper deals with a tracked robot that consists of the proposed crawler module, in which a planetary gear reducer is used as the power transmission device to give two different outputs with just one actuator. This under-actuated system could perform posture control through the interaction between the front and rear modules. On occasion, the posture that the front module is lifted up can make the robot overcome obstacles actively and easily. To find out the controllable postures, the static analysis of the robot has been conducted. In this paper, we provide the control strategy for performing the posture control, and propose the control methods including direct, indirect, and cooperative control to conduct the posture control. Experimental tests show the effectiveness of the control methods.

A snake-like robot can locomote in various environments; and it can manipulate objects when one end is fixed. A method of dynamic modeling for locomotion-manipulation of the snake-like robot is developed in order to unify the dynamic equations of two states. A virtual structure for orientation and position and the product-of-exponentials formula describe the mechanism and the kinematics of the robot. The dynamics of the robot are established in a Riemannian manifold. Furthermore, the dynamics of manipulation can be directly degenerated from those of locomotion. This method unifies the dynamics of locomotion and manipulation of the snake-like robot in the differential geometry formulation. Finally, simulation results of the method are presented.

In this paper, a mobile mechanism with driving capability and detecting function is proposed for in-pipe inspection task. Based on this mechanism, a robot is designed and fabricated. The advantage of this robot is that it has mobile ability in the pipe and detecting function for inspection, while only one DC motor is installed. This results in low energy consumption and low cost to make. The robot propels itself in the pipe under a driving mode, and it is used for finding the defect of the pipe under a detecting mode. By switching these two working modes, the robot performs the inspection task without other extra DC motors. Moreover, a velocity change mechanism is introduced to adapt the change of the payload through adjusting the incline angle of the roller. The characteristics of this mechanism are analyzed by comparison with a classical screw drive robot and a direct drive robot. Finally, basic experiments are conducted to testify the mobility and efficiency of this robot.

Robots are efficient and economic for in-pipe inspection tasks. In this paper, we deal with versatility and multifunction of in-pipe inspection robots. A versatile platform equipped with one driving motor is the main body of multifunctional mobile unit (MMU) that performs inspection tasks. We have developed three kinds of MMU by fixing different assemblies on the proposed versatile platform. MMU1 is an adaptive mobile mechanism that changes its working mode autonomously and gets over the obstacle without any extra motorpsilas help, in the case that the pipe diameter changes. MMU2 is a mechanism that has both driving ability and detecting function; MMU3 is equipped with assemblies that integrate the wheel and propeller function together, thus, MMU3 is able to propel both in dry pipe and watery pipe. These MMUs are all constructed from a same platform, which makes little increase of the cost but realizes of more kinds of robots. Several basic experiments have been conducted to confirm the effectiveness and mobility of the MMUs.

A robot, which is composed of adaptive mobile mechanism, is developed for the purpose of performing the internal inspection tasks of pipelines. Adaptability and efficiency are the basic considerations for this robot. Based on these concepts, a prototype is designed and fabricated. The proposed adaptive mobile mechanism equipped with one actuator can perform two working modes, a normal working mode and an assistant enhanced mode. Robot under the normal working mode is used for moving in pipe or monitoring the inner surface of the pipe. On the other hand, robot under the assistant enhanced mode will produce a larger torque to help itself surmount an obstacle in the pipe without any other driving actuator. This special feature is achieved by applying a power transmission mechanism. The rotation problem of the stator is solved according to the calculation results of the robot kinematics. Basic experiments have been conducted to testify the adaptability and efficiency of the robot.

With 3D (3-dimensional) movement's ability and rhythmic locomotion mode, a nature snake makes itself survive in rugged terrains. The rhythmic activities of most creatures are generated by the CPG (central pattern generator). Based on this fact, the sustained-type neuron has been adopted to construct a cyclic inhibitory CPG model for a snake-like robot whose joints are perpendicularly connected in series. Having compared with the sustained-type neuron and the mutual inhibitory CPG, the cyclic inhibitory CPG was proven to generate capably rhythmic output with the least number of differential equations. In this paper, we introduce the neuron network organized by the cyclic inhibitory CPGs connected in line with unilateral excitation to control the 3D locomotion of a snake-like robot, and present the necessary condition for the CPG neuron network to sustain a rhythmic output. By implementing this control architecture to a simulator with consideration of mechanical dynamics of a real snake-like robot "Perambulator", preliminary parameter setting of the CPG neuron network for its 3D locomotion is obtained. Moreover, it is shown that "Perambulator" can successfully exhibit 3D locomotion by using the output of the proposed CPG network. The obtained results have also provided a bran new approach to understand the unknown neuron network of nature snakes

A reconfigurable modular planetary robot system (RMPRS) consists of the parent body and multiple asymmetric wheel-manipulator child-robot modules. The module, which can independently locomote and manipulate, possesses the orientation of posture and the direction of locomotion. The modules have reconfiguration capability so that a group of the modules can construct a variety of configurations. The aim of the robot reconfiguration is to generate better configuration with respect to the directional locomotion adapted to the environment. Module state vector (MSV) and configuration state matrix (CSM) are presented and constructed for representing the asymmetric module and the configurations, and supporting the transformation operation for triggering the elementary motions of the module and the reconfiguration. The algorithm for optimizing the assembly reconfiguration of discrete modules is proposed and the result is evaluated through numerical simulation in an example

The recent natural and man-made devastations have urged the research on the urban search and rescue (USAR) robot systems. This paper presents a novel shape-shifting mobile robot system named as Amoeba II (A-II) for the urban search and rescue application. It has been designed with three degrees of freedom (DOFs) and two tracked drive systems. This robot consists of two modular mobile units and a joint unit. The mobile unit is a tracked mechanism to enforce the propulsion of robot. The joint unit can transform the robot shape for getting high mobility. A-II robot not only can adapt to the environment but also can change its body corresponding to locus space. It behaves two states including the parallel state (named as II state) and the linear state (named as I state). The parallel state enables the robot with high mobility on rough ground. With the linear state the robot can climb upstairs and go through narrow space such as the pipe, cave etc. Also, the joint unit can propel the robot to roll in sidewise direction. Especially, two modular A-II robots can be connected through jointing common interfaces on the joint unit to compose a stronger shape-shifting robot, which can transform the body into four wheels-driven vehicle. Finally, the elementary experimental results validate the adaptation and its mobility

A new Reconfigurable Planetary Robot System (RPRS) is introduced in this paper. The locomotion mechanism, especially the static force analysis and the climbing ability for different configurations of the multiple child-robots are presented in detail. The basic configurations of two child-robots systems were given in three modes: connecting in series with arm in front or back and combining to a loop with grasper. The simulation results of these three configurations based on static analysis demonstrate that the climbing ability is closely correlated to their configurations. Compared the results, the conclusion can be obtained that the loop configuration has the best effect than others on slope climbing. The actual experiments of the child-robots system have illustrated the simulating results, and an exciting phenomenon has emerged, which shows that all the configurations can climb bigger gradient than the simulating results. The phenomenon rightly discloses the characteristic of the novel architecture of the child-robot.

A reconfigurable planetary rover system (RPRS) is presented, including the parent body and some child robots. The child robot composed with the arm part and the wheel part has two moving modes: locomotion mode and manipulation mode. According to the mechanical characteristics, we proposed the two methods for the motion planning of swerving locomotion. The results of experiments showed that the robot can achieve turn during locomotion by adjusting the arm's attitude. But the child robot's radius of left-hand turning motion during locomotion is bigger much than the radius of right-hand turning motion during locomotion and the effect is not obvious. The method of spot turning is presented by use of the difference between radial frictional force and tangential frictional force of ground and direction wheel, which is important for robot for autonomous locomotion.

Based on the structure of both biological snakes and snake-like robots and their rhythm locomotion, the theory of the cyclic inhibitory CPG is adopted as a control method to construct a neuron network model of the snake-like robot. The relation between the CPG parameters and the serpentine locomotion of the snake-like robot is defined in this paper. The validity of the serpentine locomotion controlled by the CPG model is verified through a snake-like robot model. The modulating methods of the CPG parameters are brought forward and simulated to realize the required turn motion and the reconfiguration. Moreover, we present that real snake-like robot can successfully exhibit serpentine locomotion by using controller output of the proposed architecture. Finally, the aspects of future researches are discussed.

Based on the structure of both biological snakes and snake-like robots and their rhythmic locomotion, the musical theory is adopted as a control method to study on a snake-like robot. The relation between the rules and symbols of the musical theory and the control process of the snake-like robot is defined in this paper. Thus the data sequence of the relative angles in the serpentine locomotion is melodized. The gait score of the serpentine locomotion is utilized to control a snake-like robot named "Perambulator-I". Finally, the aspects of the future researches are discussed.

Biological snakes' diverse locomotion modes and physiology make them supremely adapted for the ground. This paper discusses the biological snakes' locomotion mode on the diverse ground, and describes the development of a snake-like robot with the adaptability for the ground. The method to realize some locomotion modes is given. The method for detecting the characteristic of ground is proposed and identified in test.

Simulating platform plays a crucial role in multi-robot research, as a tool to quickly and efficiently test new concepts, strategies, and algorithms. In this paper, OpenGL and Visual C++ based modeling method has been discussed in detail to establish a platform for the 3D simulating of multi-link mobile robots and their collaboration. The cooperation strategies, the control methods and the communication mechanisms of multi-robot system can be explored and verified by this platform. A planetary robot system is used to verify the validity of the developed platform. The effectiveness and the practicability of the platform are successfully demonstrated by a four-robot motion coordination simulating results.

Docking is an essential function for reconfigurable planetary robot system (RPRS), it supports almost all metamorphic characteristics of the system. This paper presents a space docking method for self-reconfigurable modular robot system. The method adopts a position sensory detector (PSD) to get the space geometrical relation between modular child robots. By using the kinematics and inverse kinematics modeling of the child robot, a docking control algorithm is developed to achieve space dock automatically. To validate the method, simulation experiments were done on a platform based on OPENGL, and the simulating results were given as well.

A reconfigurable modular snake robot has been developed, which can not only move on a plane but aIso achieve some f-dimensional motions while reconfigured. Control equations of 3-dimensional locomotion were established by the composition of two bending motions in mutual orthogonal plane. Three types of lateral rolling locomotion, flapping, linear rolling and curved rolling, were achieved by controlling the amplitudes and the number of two waves in the two bending motions. Using the three types of locomotion the snake robot can realize net lateral translation, alternation of its contact base and rolling over some obstacles. The lateral rolling locomotion obtains its driving force through the interaction with the environment. The rolling shape and its direction depend on the transferring direction and phase difference of the two waves respectively.

With high adaptability to environments snakelike robots offer a variety of advantages over other mobile robots. Such a robot with passive wheels has quite different mechanism in locomotion from that of other locomotion systems. We have developed a snakelike robot for rescue applications. The unit composing the snakelike robot of Shenyang Institute of Automation (SIA) is a module including actuating system and control system. To let the snakelike robot perform turning motion and compensate offset and orientation errors of the robot, we propose an amplitude modulation method and a phase modulation method based on analysis of the serpenoid curve. The side motion of the snakelike robot can also be generated by the amplitude modulation. The tracking control method is also proposed based on sensor information. Computer simulations and experimental tests are performed to show the validity of the proposed methods.

Hyper-redundant manipulator has more degrees of freedom than the least necessary to perform a given task, thus it has the features of overcoming conventional industrial robot's limitation such as improving its kinematics and dynamic performances. Crucial as it is, effective control of hyper-redundant manipulator is difficult for its redundancy. A novel shape control technique based on the concept of variable structure regular polygon and subsystem has been proposed. This technique, using variable structure regular polygon and neural networks models, is completely capable of solving the control problem of a planar hyper-redundant manipulator with any number of links following any desired path. With regular polygon side number's variety and its shape's transformation, the manipulator's configuration changes accordingly and moves actively to perform the task form point to point or following a path. Compared with other methods to our knowledge, this technique has such superiorities as fewer control parameters, higher precision and less computation. Simulation of a six-link modularized manipulator's inspection work in a bottle-like concave has demonstrated that this control technique is available and effective.

It is essential to design a joint mechanism for snake-like robots to exhibit more mobility, no singularity and powerful actuation for many applications. By adding a series of passive wheels to the perimeter of the newly designed joint mechanism with 3 DOFs, a snake-like robot provided with the characteristic of omnidirectional mechanism can traverse rough terrain and compensate the lack of actuation due to passive wheels. The nonholonomic constraints and kinematics are analyzed as well as the redundancy. The composite motion method and grouping alternation motion control method are thus proposed for the locomotion of robot and the avoidance of singularity. Also, the grouping alternation motion adds a new explanation to the sinus lifting locomotion of natural snake. Computer simulations validate both mobility of mechanism and effectiveness of control methods.

Biological snakes' diverse locomotion modes and physiology make them supremely adapted for environment. The special structure of snakes and their unique movement offer them peculiar ability of climbing and moving even in some ill-conditioned environments such as on the marshland or in narrow tubes. In this paper, we first discuss the controllability of a 3-dimensional snake-like robot, and then show the controllability of the robot by computer simulation.

Biological snakes' diverse locomotion modes and physiology make them supremely adapted for environment. To realize these snakes' noticeable features, we have developed a snake-like robot that has no any forward direction driving force. To enlarge the environment-adaptable ability of our robot, in this study we discuss the creeping locomotion of our snake-like robot on a slope. A computer simulator is presented for analysis of the creeping locomotion of our snake-like robot on a slope, and the environment-adaptable body shape for the creeping locomotion of the snake-like robot on slope is also derived through this simulator.