Principle:ARISE Initiative Robosuite Signal Buffering
| Knowledge Sources | |
|---|---|
| Domains | Robotics, Signal_Processing |
| Last Updated | 2026-02-15 07:00 GMT |
Overview
Fixed-length data buffers that store recent signal values for computing running averages, deltas, and delayed readings in control loops.
Description
Control systems frequently require access not just to the current sensor reading but also to recent historical values. A ring buffer (circular buffer) maintains a fixed-size window of the most recent entries, automatically overwriting the oldest entry when a new one is pushed. This structure is essential for filtering noisy signals -- for example, computing a moving average over the last N velocity readings to smooth the derivative term in a PID controller.
Three buffer variants address different use cases. A ring buffer stores a configurable number of past values and provides a running average across all stored entries. A delta buffer tracks exactly two values (current and previous) and computes their difference, which is useful for calculating finite-difference derivatives of sensor readings. A delay buffer extends the ring buffer to return values from a specified number of steps in the past, enabling simulation of sensor latency or communication delays.
All buffer types operate on multi-dimensional numerical data (vectors), making them suitable for joint-space quantities (e.g., joint positions, velocities) as well as task-space quantities (e.g., Cartesian positions, forces). The buffer dimension is fixed at construction time, and all operations run in constant time regardless of buffer length.
Usage
Use ring buffers when a controller needs smoothed (averaged) signals, such as filtering the derivative component of a PID controller or computing a running average of force-torque sensor data. Use delta buffers when you need the instantaneous change between consecutive readings, such as computing velocity from position samples. Use delay buffers when simulating communication latency or when a control algorithm requires access to a value from a known number of timesteps ago.
Theoretical Basis
Ring Buffer (Circular Buffer):
A ring buffer of length L and dimension d stores values in a 2D array buf[L, d] with a write pointer ptr:
push(value):
ptr = (ptr + 1) mod L
buf[ptr] = value
average = mean(buf[0:size]) # size = min(num_pushes, L)
current = buf[ptr]
This provides O(1) insertion and O(L) averaging. The running average acts as a low-pass filter with a rectangular window, attenuating high-frequency noise proportional to 1/L.
Delta Buffer:
A two-element buffer tracking current and previous values:
push(value):
last = current
current = value
delta = current - last
average = (current + last) / 2
The delta computation is equivalent to a first-order finite difference, approximating the discrete derivative of the signal.
Delay Buffer:
Extends the ring buffer with index-offset retrieval:
get_delayed_value(delay):
return buf[(ptr - delay) mod L]
This enables retrieval of values from delay timesteps ago in O(1) time, useful for modeling sensor or actuator transport delays in the control loop.