KOJIRO- World’s first robot with a spine!

Forget ASIMO with his awkward movements and non-expressive face. We now have the first of a kind robot with human spinal cord. The robot is developed by the evangelists at www.jsk.t.u-tokyo.ac.jp, University of Tokyo. The robot moves its hands, legs and other parts like humans do…with the help of tendons. These kinds of robots are called anthropmimetic humanoids. The robot is a step forward in the quest to build robots which look and move like humans.

The robot can be controlled using a PS2 controller. It has a spinal cord which allows the robot to bend forward as well as backwards. Kojiro is very flexible and can also arch sideways and twist its torso.  And to add to the robot’s flexibility, it can also bend its hips! Until now all humanoid robots, including ASIMO, had articulated limbs which could move with the help of DC motors connected at the joints. The older generation robots did have a good range of motion but lacked in fineness. This posed a difficulty when robot-human interaction took place.

Kojiro uses the same old trusted DC motors. But in Kojiro’s body, the motors are attached to cables. These cables in turn are attached to particular locations in the body. The muscles in human body are attached at ends to the bones. For example, there are two muscles in our upper hand; biceps and triceps. If we want to lift our hand, the biceps relax and the triceps extend. The same concept is used to move Kojiro’s hand. Kojiro has tendon muscle structures which contract or relax according to the rotation of motors. There are about 100 tendon muscle structures working together to give 60 degrees of freedom. This many degrees of freedom could not be achieved with the prior technique which had motorized joints.


Kojiro has lightweight, high performance DC motors. These motors are brush-less motors and are very small in size (0.6 inches diameter and 2.5 inches in length). Even though the motors seem to be small, they are capable of delivering about 40 watts of output power. Every single motor is controlled by a rotary encoder, tension sensor, temperature and current sensing circuit. The current fed to the motor is adjusted by a driver circuit board depending upon the temperature sensors. Controllers get all the data transmitted to the computer wherein they can see the mechanics of the robot in real-time.
The control screen is developed by Takanishi Lab.
Kojiro is mostly made up of light and flexible materials making the robot safe. The limb and posture movements are continuously monitored by embedded joint angle sensors. These sensors are situated on the spherical joints. Along with the joint angle sensors, the robot is equipped with six force sensors on the ankles. Three gyros and three axis accelerometer keep the robot balanced.

All this seems simple but is very difficult for the robot controller to be precise and accurate in movements. The team at JSK is designing control algorithms for Kojiro by attempting an iterative learning process. The robot is allowed to do some very simple moves. When the degree of accuracy is achieved, the controller goes for more complex moves by adjusting the control parameters. As for now the muscle tendon structure is autonomous only for limited movements. Further research is going on to have an integrated movement system encompassing all parts of the body.

So hone your handshaking etiquette and be prepared to get a rap from Kojiro if you get them wrong!