"Slim-Slime" is a pneumatically driven robot with a body composed of segmented modules. Each module has three flexible pneumatic actuators that allow it to bend and stretch. Through various gaits, the robot can achieve different motions.
http://www-robot.mes.titech.ac.jp/robot/snake/slim_slime/slim_slime_e.html
The biorobotics laboratory at CMU has a major project on modular serpentine locomotion. With their various designs, they have been able to climb stairs and pipes, swim through water, and traverse uneven terrain.
http://voronoi.sbp.ri.cmu.edu/projects/modsnake/modsnake.html
Videos!
JPL has been developing a serpentine like robot with angular swivel joints for visual inspection in outerspace.
http://robotics.jpl.nasa.gov/tasks/rsi/accomplishments/snake/snake.html
The Inchworm is a biologically-inspired mobile robot whose movement is similar to that of an inchworm caterpillar. It consists of a three DOF body which can flex and extend to propel itself, along with electromagnets at each end of the body which provide the anchoring force for the motion.
http://www.cs.dartmouth.edu/~robotlab/robotlab/robots/inchworm/
"Hyperion" is a very small and lightweight four-legged robot that can climb walls. It uses suction cups to stick to surfaces. It also has a reduced DOF (only 3), showing that many actuators is not absolutely necessary.
http://www-robot.mes.titech.ac.jp/robot/walking/hyperion/hyperion_e.html
The LEMUR robot was invented at NASA-JPL. The LEMUR IIb is a 4-legged modification by Tim Bretl, which is capable of 3D motion (it has 22 DOF). His motion planners are trying to mimic human rock-climbers.
Developed at iRobot and the polyPEDAL lab at UC Berkeley, the Mech-Gecko mimics the gecko's "sticky" feet, allowing it to climb up walls and on ceilings.
This is a common type of mechatronic quadruped. It has four legs, each with 3 DOF active joints.
XEVIUS is a simple example of a robot that changes its shape to adapt to different terrain.
http://www-robot.mes.titech.ac.jp/robot/wheeled/xevius/xevius_e.html
Sprawl is a hexapod insect-like robot (biomimetic), designed to move quickly over relatively level terrain.
Octopus is able to crawl over very rough terrain and even climb steps that are taller than itself. It also uses an ingeniusly simple tactile wheel sensor array. Using IR sensors placed around the inside of the wheel, it can detect the direction of a contact force.
Rhex is a cockroach-like robot that has been designed to crawl over very uneven terrain. It is also capable of climbing slopes and stairs, hopping, and turning itself over.
http://ai.eecs.umich.edu/RHex/ProjectOverview.html
http://www.rhex.net
Tri-Star III is a desing for an autonomous space exploration robot. The interesting feature of this robot is that its wheels are expandable, making it much easier to adapt to terrain.
http://www-robot.mes.titech.ac.jp/robot/spaceprobe/tristar/tristar_e.html
There are three versions of the Thes robot, each designed to travel through gas pipes, including angled pipes. They each have wheels attached to springs that press against the walls of the pipe.
http://www-robot.mes.titech.ac.jp/robot/wheeled/thes/thes_e.html
The MRINSPECT robots were designed to study Non-Destructive Testing inside pipes. They are similar to the Thes robots above, but include more robust differential drive wheels.
Research at the Technion in Israel has focused on locomotion with quasi-static forces. They have built various spider-robots that crawl through tunnel-like environments. It stabilizes itself against the tunnel walls before each movement.
This 8-legged spider robot can autonomously climb through planar pipes. It also exhibits reflexive and reactive behavior.
The mechanical control and workings of this robot are completely contained within a sphere. Because of this design, it can easily be made liquid and gas proof. It also recovers easily from collisions and the robot can not turn over or fall down.
http://www.automation.hut.fi/research/robotics/ball/ballrob.htm
This robot is capable of rough terrain locomotion by rolling and jumping. It has a deformable soft body and flexible actuators and can roll and jump on the ground simply by changing the shape of its body.
http://www.ritsumei.ac.jp/se/~hirai/research/softrobot-e.html
Gyrover is a single-wheel robot that is stabilized and steered by means of an internal, mechanical gyroscope. Gyrover can stand and turn in place, move deliberately at low speed, climb moderate grades, and move stably on rough terrain at high speeds.
This robot starts out as a ball and expands "spiny" wheels, allowing it to drive over rough terrain.
