Building a Smarter Robot Leg

One of our recent projects at Cape Cod Makers has been attempting to design a robot leg that can sense a bit of the world around it. Currently we have a Hexapod robot (6 legged walking robot) which can walk on flat surfaces. However if you wanted to build a robot to move on flat surfaces, a wheeled robot is a much better choice. It’s faster, easier to control, and much more power efficient (i.e. fuel efficient). There is a big reason why we drive cars instead of six legged mechs to work. Where a walking robot really outperforms is on uneven terrain. Take the simple case of walking up stairs. A wheeled robot has no chance of going up stairs while we ourselves are proof that walking robots can succeed. A walking robot needs to handle uneven terrain. Unfortunately when we try to walk our hexapod on uneven terrain it generally ends in absolute failure. As it walks, it moves its legs to positions that would be touching the ground on a flat surface, but are often hanging in mid-air when walking on an uneven surface. The problem is that the robot can’t sense when a leg is supporting its weight or not. It also can’t tell if a leg is stuck on terrain while trying to move. Our goal is to develop a Leg Controller which can use feedback from the leg to better control it.

Our robot legs are composed of three 3D printed parts, a hip, femur, and tibia. These are connected using servos as the joints. Two of the servos work together to create a hip joint (one providing rotation for the leg, the other raising and lowering the femur), while the last servo connects the femur to the tibia creating a knee joint. To provide feedback we have connected the power for each each servo through a high-side current sensor and used modified servos that provide a analog feedback from the internal potentiometer of the servo. The current sensors let you know if a servo is being blocked by something, like the ground or some obstruction, while the analog feedback tells you the actual angle the servo is at as opposed to the angle it is being directed to achieve. Connecting these sensors and the servos is a PIC18F24K22 8-bit microprocessor which handles driving the servos, communicating with the current sensors, and reading the analog feedback signals with its ADC. Now the real challenge begins as we try to tie the sensor information with the servo control to create something a bit smarter….

If you have any questions or suggestions we would love to hear them, or come to one of our meetups to see the leg in action!

 

 

Posted in Project

The Robots of Robot Beach Party 2017

Wilson Barnstable High School

Wilson
Barnstable High School

Vex God Mashpee High School

Vex God
Mashpee High School

Pod2K17 Monomoy High School

Pod2K17
Monomoy High School

Techno Mashpee High School

Techno
Mashpee High School

Slartibartfast Nantucket High School

Slartibartfast
Nantucket High School

R2 Kittie Mobile MakerSpace Cape Cod

R2 Kittie
Mobile MakerSpace Cape Cod

Psycho Mashpee High School

Psycho
Mashpee High School

Not an Egg-Bot Sherpa Engineering

Not an Egg-Bot
Sherpa Engineering

Mr. Lenda Had A Name Barnstable High School

Mr. Lenda Had A Name
Barnstable High School

Last Minute Barnstable High School

Last Minute
Barnstable High School

Land Eagle CC Regional Technical HS

Land Eagle
CC Regional Technical HS

Dexter CC Regional Technical HS

Dexter
CC Regional Technical HS

Canalman Bourne High School

Canalman
Bourne High School

BRIM2 Marzoratti Family

BRIM2
Marzoratti Family

BBX172 Mashpee High School

BBX172
Mashpee High School

Prime Meridian CC Regional Technical HS

Prime Meridian
CC Regional Technical HS

Yogi Upper CC Regional Tech School

Yogi
Upper CC Regional Tech School

McRibz Upper CC Regional Tech School

McRibz
Upper CC Regional Tech School

Posted in Robot Beach Party

Robot Beach Party 2017 Results

Thanks to all the teams this year for competing. It was great watching all the robots!

Robot Beach Party 2017 Results

Posted in Makerfaire, Robot Beach Party