Use a laptop as the FCI workstation

[rickstaa]

Can I use my laptop as the FCI workstation?

[rickstaa]

I performed several tests to see if I could use my laptop as the FCI workstation to performing real-time control. In the end, after performing some tests and asking advice from Gijs van der Hoorn I came to the conclusion that my laptop is not suited for this purpose. To quote Gijs:

Laptops are not very well suited for running workloads with determinism requirements in general, simply because they tend to be designed for good mobility, which means lots of power management and other tricks to flexibly assign resources to where they are needed. Both at the OS level, as well as the firmware/hardware level.

In our setup where mobility was required we therefore bought a SBC for real-time performance control. On the other hand, the SBC for the FCI doesn't have very high processing requirements. What it needs are a low-latency, low-jitter connection, with deterministic performance. Additionally, we also bought a second SBC for performing other calculations like RL network inference.

Performed tests

System info

I performed all the tests below on the following system:

OS: Ubuntu 20.04
Default kernel: 5.8.0-53
PC: HP Zbook G5 Studio x360
RAM: 2x32 GB Samsung M471A4G43MB1-CTD geheugenmodule 32 GB DDR4 2666 MHz
GPU: Nvidia Quadro P1000
CPU: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz

Network and performance tests

To see if the robot could be controlled in real-time from my laptop, I performed the network tests that are given in the panda documentation.

Simple ping test

[1621600461.833791] 1208 bytes from 172.16.0.2: icmp_seq=10000 ttl=64 time=0.480 ms

--- 172.16.0.2 ping statistics ---
10000 packets transmitted, 10000 received, 0% packet loss, time 9999ms
rtt min/avg/max/mdev = 0.183/0.512/0.773/0.072 ms

We can see from the results above, we can see that the mean round-trip time is 0.512ms, and the max round-trip time is 0.773ms. Judging from the fact that the documentation achieves a max round-trip time of 0.5ms and states that the total control time has to be under 1ms, it might be that my network card in my laptop is too slow for real-time control. Let's perform the libfranka/build/examples/communication_test to see if this is the case.

Communication test

#9900 Current success rate: 0.59

Finished test, shutting down example.

#######################################################
The control loop did not get executed 73 times in the
last 10000 milliseconds! (lost 73 robot states)

Control command success rate of 9927 samples: 
Max: 1.00
Avg: 0.49
Min: 0.28

WARNING: THIS SETUP IS PROBABLY NOT SUFFICIENT FOR FCI!
PLEASE TRY OUT A DIFFERENT PC / NIC
#######################################################

My laptop is probably not sufficient enough to serve as a real-time control interface from the results above.

What to do instead

You can check this discussion post for what to do if your laptop is not sufficient enough.