sichitong / linux-robotic-arm

A scalable Linux robotic arm userspace application using forward kinematics and inverse kinematics in a threaded control framework

Linux-Robotic-Arm

The demo and application models a 2RR arm on a Intel Edison system running Linux.

It makes use of inverse and forward kinematics calculations on different position sensors in order to obtain the rotor angular state, and then spawns unique control threads per joint in order to keep the joints to the reference/target angle value.

Layered SW Architecture

Class Structure

A robot joint is formed by a positioning (imaging/encoder) and movement (actuator/motor) objects, by having this abstraction we can make a robotic arm operate with different layers and or objects.

Testing has shown and we would recomend tweak the following parameters in the Linux scheduler through the sysctl.conf interface in order to get better response times.

kernel.sched_tunable_scaling = 0
kernel.sched_latency_ns = 120000
kernel.sched_min_granularity_ns = 200000
kernel.sched_wakeup_granularity_ns = 1000
kernel.sched_migration_cost_ns = 100000

As well as disabling C-States and P-States on the board by using

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state1/disable
echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state2/disable
echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state3/disable
echo 1 > /sys/devices/system/cpu/cpu0/cpuidle/state4/disable

And also install irqbalance for a more responsive experience on multi-core systems.

I have tested the above parameters in an Intel Edison and an Intel Galileo board.

Contributors: Omar X. Avelar Juan C. Razo