Project Information


Grinder is a multimimodal hexapod robot, capable of both walking and skating on its passive wheels. It is built with Dynamixel MX64T / MX28T and is capable of walking with several different gaits, including lost leg detection and compensation, plus skating on passive wheels when the legs are spread.
Created by psyclops | Forum Thread Link | External Link
11 months
20-50 pounds
700mm L x 500mm W x 400mm H
1-2 hours
Autonomous python code with PS3 SixAxis override
Powersource: LiPO / LiON

2x 5000MAh 4s Lipo Hardpack

Locomotion: Hexapod

Hexapod walking but also skating on passive inline skate wheels

Controller/CPU: Advantech MIO-2261 Intel Atom 1.8GHz

Advantech MIO-2261 Intel Atom N2800 Dual Core1.8GHz, 4GB RAM, 32GB SSD, Bluetooth/Wifi combo card


2x HD camera, 2x LV MaxSonar sensors, 1x Ping Sonar sensor


12x MX64T (6 leg forward/backward X axis, 6 leg up Z axis), 8x MX28T (6x leg out Y axis, 2x head pan/tilt)


Grinder represents the next evolution in my design for a hexapod robot, building on the locking
linkage design that was so successful on Ziggy.
The motors that hold the
robot up (the inner motors seen in the photo) are connected to the legs by two linkages that are
driven inline when the leg meets the ground. In this way, no force is transmitted back to the
motor when the leg is down and the robot can stand without needing to energize the motors. This
makes for a very energy efficient robot and has the added advantage that walking is still possible
when a motor is not working.

I had been thinking for several years about building a new robot with the added third degree of
freedom (DOF) on each leg that would allow the foot to move to any arbitrary position within its
3D envelope. When Ziggy lost the Walker Challenge, a competition that the robot had dominated
for 8 years, at RoboGames 2012 I decided it was time to build that robot and retake my medal.

After an intense year of design, redesign, fabrication, assembly and programming I had Grinder
ready for RoboGames 2013, held on 4/19/13 - 4/21/13 in San Mateo, California. In the Walker
Challenge he easily beat out the competition with a time of 7.75s to complete the course - see
the video of him winning below. The Silver medal time was 14.82s so he
was nearly twice as fast, clocking in a speed of almost 0.4 m/s.

Grinder also won the Silver Medal in Best of Show, losing by a mere 2 points to my friend
Nicolas Saugnier and his great robot

What makes Grinder unusual is that, when his legs are spread wide, the passive inline skate wheels
engage and with a swimming motion the robot can skate at a reasonable speed on any flat surface.
By modifying the motion steering can be achieved, so Grinder can negotiate obstacles while skating
at speed. He can skate over 10x as fast as he can walk.

Now the competition is over I will have time to rewrite the robot's software to add in Inverse
Kinematics, localization using both stereoscopic cameras and sonar sensors and a variety of
new behaviours. Watch this space!

You can view Grinder's page at - not much up yet but I'll be adding info as I go.

Video of the robot skating:

Video of winning the Walker Challenge:

Video of the ripple gait: