Get Actual Joint Positions History
SUMMARY
Get Actual Joint Positions History returns joint positions from the controller's internal history buffer, allowing you to look back a specified number of control steps.
This skill is useful for computing finite-difference velocities, detecting motion lag, or reconstructing a recent trajectory segment.
SUPPORTED ROBOTS
This skill is currently supported on Universal Robots only. Calling this method on other robot brands will raise a NotImplementedError.
The Skill
history = robot.get_actual_joint_positions_history(steps=5)The Code
Example: Read Joint Position History
Connect to the robot and read the last 5 control-step joint configurations.
from loguru import logger
from telekinesis.synapse.robots.manipulators import universal_robots
robot_ip = "192.168.1.2" # replace with your robot's IP
robot = universal_robots.UniversalRobotsUR10E()
# Connect
robot.connect(ip=robot_ip)
steps = 5
history = robot.get_actual_joint_positions_history(steps=steps)
logger.success(f"Joint positions history ({steps} steps): {history}")
# Disconnect
robot.disconnect()The Explanation of the Code
get_actual_joint_positions_history reads the actual_joint_positions_history_0 through actual_joint_positions_history_N fields from the RTDE data stream. The steps parameter controls how many past control cycles to retrieve. The returned data is ordered from the oldest to the most recent entry.
How to Tune the Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
steps | int | 0 | Number of past control steps to retrieve. A value of 0 returns only the most recent sample. |
Return Value
| Type | Description |
|---|---|
list[float] | Joint positions across the requested history window, flattened or structured depending on the number of steps. |
Where to Use the Skill
- Finite-difference velocity estimation — Compute joint velocity from two consecutive position samples
- Trajectory reconstruction — Replay a short window of recent motion for logging or analysis
- Lag detection — Compare history positions with commanded positions to measure control latency
When Not to Use the Skill
Do not use Get Actual Joint Positions History when:
- Only the current state is needed — use Get Joint Positions for a single current reading
- You need velocity data directly — use Get Actual Joint Velocities instead