intorduction

S-curve planning is a common practice in robotics and mechanical systems for calculating speed or position trajectories. In my case, I am running my code on a limited CPU (TMS320F280) without floating point unit and I want to avoid floating-point calculations by using Texas Instruments' fixed-point library, "IQmathLib".

"IQmath" library has a lot of basic operations, such as sqrt, but does not include a third root, so i had to implement a "cube_root_fast" function on 32-bit numbers, assuming 24 bit of fixed-point fraction and 8 bit of signed integer

debugging in vscode

First of all, I don't have any expertise in C debuggers, and they seem somewhat magical to me. Anyway, this repository has a normal Makefile and can be debugged using VSCode's Makefile Tools extension.

Keep in mind that all numbers have 24 bits of fixed precision, and to see their real values in debugger you should divide them by 16777216.0.

other repos

• s-curve implementation in rust
• s-curve implementation in python

exmple

in the above image you can see 3 example calculations

blue:

• travel_distance and jerk are small
• can't reach max_acceleration an max_speed conditions

green:

• travel_distance and jerk are bigger
• max_acceleration and max_speed conditions can be reached

orange:

• travel_distance is small and jerk is big
• can reach max_acceleration but can't reach max_speed

Notice:
plot drawing code and some other codes are not included here, sorry that's all i can share.