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Kondo Kagaku Co., leading Japanese maker of Radio Controlled (RC) technology, realized at the end of 2002 that one of its high powered—low weight digital servos, the PDS-2144FET, designed to maneuver RC airplanes and RC race cars, was being sold to individuals in unlikely large quantities of 20-30 at a time and was consistently out of stock at retail stores. The price of this particular servo was in excess of US$100 each and normally only a couple were required for the average RC project.

Home made, RC-Servo driven
humanoid robot

Eventually Kondo realized that the servo was used to build the limbs and muscles of a new brand of humanoid robots. PDS-2144FET had a high torque of 13kg/cm and a high rotation speed of 77rpm (the common metrics in the RC world in this case would be 0.13sec for a 60° turn) and this combination was particularly good at creating sturdy abrupt robot movements without the limbs wobbling about when coming to a halt. Since then, what started as an underground movement of robot hobbyists, turned into a popular televised Japanese/Korean tournament called “Robo-One” where people bring their servo-driven humanoid robot creations to compete and fight against each other.


Pictures from Robo-One Tournament

This was an opportunity for Kondo to enter into the new and promising market of personal robotics. Kondo gripped the opportunity with both hands and created a new line of servos particularly suited for Robo-One robots. These servos had two sided hones to allow a better grip of the brackets that define the robot’s structure and connect one servo to another.

In addition, the digital servo’s internal controller required a new function. It had to be able to report the motor’s relative position to a remote PC in order to ease the process of teaching the robot to perform complex movements. The new servo was named KRS-784ICS and is the first in a servo line called “Red Version”. To make the kit affordable, KRS-784ICS has only 8.7kg/cm and a speed of 60° @ 0.17 sec but it weighs only 45g and its retail price is US$50.

This also gave birth to a new PIC (8-bit CPU) based controller called RCB-1 that comes with 128kb of memory for storing pre-learned movement sequences (used in autonomous mode) and interfaces with a PC through an RS232 connector. This connector can also be used to interface to an onboard BlueTooth board or to a more powerful CPU board such as Gumstix.

Kondo’s ultimate objective was to create a Robo-One type robot kit that would not only be good looking and host high quality parts, materials and manufacturing standards but it also had to be easy to assemble, allow for long lasting battery time, it had to reach record breaking agility and it had to be affordable.

The KHR-1 kit answered all the above requirements. It has 17 servos and can run for a full hour before requiring a recharge. It comes with a couple of windows GUI based programs. The first one, called ServoManageR, is used to program each of the servo’s intrinsic parameters. These are saved onto the servo’s flash memory. The second program is called HeartToHeart and allows the robot to learn movement sequences. Each movement is composed of consecutive “poses” that are recorded and the transition between the poses can be as slow or fast as the user desires to achieve a realistic looking performance.

KHR-1 is the first kit robot of its kind to have a relatively low price tag. Its servos double as sensors because they can relay their current position and torque to the controller/PC even though the bundled software does not make use of this feature yet. When RCB-1 is in non-autonomous mode ie: controlled by the remote PC or a more powerful secondary onboard CPU/controller, KHR-1 can perform feedback driven movements such as balancing and running and serve as a platform for more advanced Artificial Intelligence.

The usual way a digital servo works is through a PWM signal. The PWM signal is composed of 20 millisecond intervals. ICS servo returns the current location on a signal gaps between the pulse width. The controller receives this way, the current position of the servo's potentiometer. Digital Servos used for Remote-Control (RC) of airplanes and cars usually don't need any feedback. The feedback mechanism is the human holding the fancy remote control and joysticks. A walking robot has more complex requirements. In addition, the servos have power limiting functions that can throttle down the power when the servo is blocked.

GUI helps in recording robot's 17 servo relative positions

More software is under development including an open-source project to allow researchers to exploit the functionality of RCB-1 and the “Red Version” servos in new ways. KHR-1’s functionality will evolve through new software and hardware upgrades.

Kondo recently introduced an additional servo to the ICS "Red Version" servo family. It is compatible in size and weight with the KRS-784ICS found in the KHR-1 kit but has additional torque of 20kg/cm and metal gear. This allows the robot to withstand higher weights and terrain challenges.

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