scatti

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Pronunciation: Italian /ˈskat.ti/ — scatti means "bursts / jolts" (rapid movements), fitting a jerk-limited motion generator.

Pure C99 port of Ruckig — real-time jerk-limited trajectory generation.

Features

• Pure C99, zero third-party dependencies, portable to bare-metal / RT kernels (LinuxCNC RTAPI).
• Arbitrary DOF, position / velocity control, three synchronization modes (time / phase / independent).
• 3rd / 2nd / 1st order models, asymmetric velocity and acceleration limits.
• Full Ruckig Pro feature set: intermediate waypoints, per-section constraints, position bounds, computation interrupts (microsecond budgets).
• 3-level CMake optimization switch (-DSCATTI_OPT_LEVEL={0,1,2}).
• Optional musl cube root + overridable memory macros for libm-free / RTAPI embedded environments.
• Out-of-the-box Python (cffi) + Rust (bindgen) bindings.

_{Smooth position + bounded acceleration + piecewise-constant jerk — 3-DOF, 500 Hz real-time generation.}

Performance

7-DOF mean / end-to-end (µs):

Version	Mean	End-to-end
Ruckig C++ -O3	6.65	7.55
Ruckig C++ -O3 -march=native -flto (fair)	6.46	7.34
scatti L2 (libm cbrt)	6.19	7.08
scatti L2 + fast cbrt (musl replaces libm)	6.03	6.93

scatti L2 is 7% faster on average than fairly-compiled Ruckig, ~9% faster than the default Release build. The built-in musl cbrt adds another 2-3% and removes the libm dependency — suitable for RT kernels.

DOF scaling (fast cbrt mode, same machine):

DOFs	Mean (µs)	End-to-end (µs)
3	2.24	2.69
7	6.04	6.94
14	12.76	14.15

Numerical consistency

Cross-checked against C++ Ruckig over 99,344 random trajectories; both libm and fast-cbrt configurations are bit-identical:

Metric	Result
Match rate	100.00%
Max duration diff	4.55e-13 s
Max position diff	5.90e-12
Max velocity diff	9.24e-14

Quick start

cmake -B build -DSCATTI_OPT_LEVEL=1
cmake --build build -j
sudo cmake --install build      # or: cd build && cpack   to build a .deb

Minimal usage:

#include <scatti/scatti.h>

CRuckig *otg = scatti_create(3, 0.01);       /* 3 DOF, 10 ms cycle */
CRuckigInputParameter *in  = scatti_input_create(3);
CRuckigOutputParameter *out = scatti_output_create(3);

in->current_position[0] = 0.0;  in->target_position[0] = 5.0;
in->max_velocity[0]     = 3.0;
in->max_acceleration[0] = 3.0;
in->max_jerk[0]         = 4.0;
/* fill the remaining DOFs the same way */

while (scatti_update(otg, in, out) == CRuckigWorking) {
    /* drive the actuator: out->new_position / new_velocity / new_acceleration */
    scatti_output_pass_to_input(out, in);
}

scatti_output_destroy(out);
scatti_input_destroy(in);
scatti_destroy(otg);

Headers live in include/scatti/; the full API and Pro fields are documented in the corresponding header comments.

CMake integration:

add_subdirectory(scatti)
target_link_libraries(your_target PRIVATE scatti m)

Acknowledgements

Based on Ruckig by Lars Berscheid (original C++ implementation, Community Edition).

Paper: Berscheid, L., & Kroeger, T. (2021). Jerk-limited Real-time Trajectory Generation with Arbitrary Target States. Robotics: Science and Systems (RSS). arXiv:2105.04830

License

MIT (same as Ruckig Community Edition).