MODULE 28 / PHYSICAL WORKSHOP
Commission one layer at a time
Rehearse sensor, joint and command checks in an offline mock. Then plan physical tests that add one uncertainty at a time, beginning with a securely supported single joint.
By the end, you can…
- Detect invalid and stale mock data
- Explain calibration and plausibility limits
- Write a staged commissioning test card
Power and communication
Sensor frames
Walking experiments
τ = Kp(qtarget − q) − Kd·velocityCommissioning establishes meaning
Before asking a robot to walk, establish that each measurement and command means what the program expects. Which physical joint is Left_Knee? Does positive measured angle match the model’s positive direction? Where is zero? Does the IMU report the expected quaternion order and coordinate frame? These are calibration questions to resolve in controlled stages.
A plausible value can still be wrong. Reversing a sign can turn +0.2 rad into −0.2 rad, both within the valid range. A bounds check cannot reveal which direction the physical joint actually moved. A known-direction, small-motion calibration with a supported assembly supplies that evidence.
Freshness belongs in the measurement contract
A reading may be finite and correctly scaled but too old. Save an acquisition timestamp and compare its age with control time using a consistent clock. An unchanged value does not necessarily mean a stationary joint; communication may have stopped. Commands also need age checks so a disconnected controller does not silently preserve a motion request.
The lesson mock rejects stale, future-dated, nonfinite and out-of-range values. Its 0.1-second age threshold and ±0.8-radian bounds are arbitrary teaching settings, not approved BDX-R limits. Physical thresholds must follow actual hardware, operating mode and stopping behavior.
Stopping has several meanings
A zero speed command asks the policy to stop translating or turning, while joints may still balance actively. Pausing simulation freezes numerical time. Disabling torque removes active support and can let a robot collapse. Removing power is another physical action with system-dependent consequences. A button label alone does not establish the outcome.
Write the response for each fault and operating state. A supported single joint, suspended assembly and standing robot have different mechanical conditions. Test the real stop path during early controlled stages. A software exception handler does not replace an independently understood physical power/control arrangement.
Use observable gates between stages
Begin with documentation and secure support, then communication and sensor checks with motor power controlled. Establish direction and zero in a limited single-joint test. Add a subassembly, inspect cable clearance and movement, then supported full-body poses. Standing and short walking/stopping trials follow those checks.
The upstream hardware backend can initialize and enable devices during construction. Do not instantiate it merely to inspect behavior. Read its source and use the separate offline mock. A future Jetson installation must match its board, operating-system image and dependencies; copying the Mac virtual environment is not a deployment procedure.
WORDS YOU NOW KNOW
- Commissioning
- Establishing that an assembled system behaves as specified through staged checks.
- Calibration
- Determining the relationship between measurements/commands and physical quantities.
- Stale data
- A measurement too old for the current decision.
YOUR CALL
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Primary references for this module. Use the version and hardware revision named in the lesson.
Hardware startup behaviorPinned IMU implementationVersioned Jetson setup referenceChoose the guide matching the actual board/image.Download offline mock