Ghost Minitaur - The Springy Robot
Written by Harry Fairhead   
Sunday, 25 September 2016

Ghost Minitaur is a clever design for a robot and it is great fun to watch. You can buy one for even more fun. 

This particular robot takes a very different approach to locomotion. It has legs yes but they aren't driven by gears. Instead the motors are directly connected to the legs. This direct drive approach has lots of advantages.There are no fragile gears with backlash and play to get in the way of accurate positioning. The motor current can be used as a direct feedback of what force the motor is exerting. It is also easier to use the motor to apply a force without needing rotation or even any movement of the shaft. This effectively creates an electromechanical spring or muscle depending on how you look at it. This is why Ghost Minitaur seems to be so "springy".

Now take a look at the video and be impressed: 


The downside of using direct drive is that the motor has to be carefully selected. It has to generate enough torque to be useful even when stalled and without the help of gears. Then there is the small matter that most motors aren't designed to be run in a permanently stalled mode. However, it seems that these problems are worth overcoming because of - well you can see - the bouncy springy behavior that the robot is capable of.  

Its specs are:


Length (hip to hip): 0.4 m

Width (toe to toe, standing height): 0.28 m

Mass: 6 kg

Payload: 3kg

Endurance: 20 minutes (heavy use)


Running speed: 2.0 m/s

Turning speed: 1 rad/s

Sideways crabbing speed: 0.04 m/s

Vertical jump displacement: 0.48 m



The good news is that you can buy a Minitaur and use it for experiments in gait, i.e. bouncing around, or as a sensor platform.
Given how terrible most robot platforms are at moving around a domestic environment I would think that a Minitaur would do better than say a robot vac or a mower at both jobs.

The bad news is that the current manufacturing is only for small batches so the price tag is $10,000. It is estimated that this could fall to less than $1500 with enough volume. 




The whole idea of motors as software controlled springs and actuators sounds like a good one. So I hope Minitaur does take off.

More Information


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Last Updated ( Sunday, 25 September 2016 )