Danger Settings

Everything below the red "DANGERZONE" divider in the "Stretcher" panel controls the hardware limits and firmware behaviour of the device. These values match your physical setup and the firmware on the controller.

Movement limits

These values define how far the arms are allowed to travel. They are given in the raw position units of the device.

The "Left Arm X Max" and "Left Arm X Min" set the upper and lower X position limits for the left arm, and the "Right Arm X Max" and "Right Arm X Min" do the same for the right arm. The "Y Max" and "Y Min" set the upper and lower limits for the Y axis. The "Min Distance Between Arm Mounts" is the smallest distance the two arm mounts are allowed to have between them.

Calibration and geometry

These values describe the physical geometry of the device and how steps translate into movement. They are given in micrometers (µm).

The "Micrometers Per Step" is how many micrometers a single step moves. You can determine it by comparing how far the arms physically travel against how many steps the motors took:

1. Measure the distance between the arms.

2. Stretch or contract the arms by a known number of steps using the distance slider, and note how much the motor positions change.

3. Measure the distance between the arms again.

4. Divide the change in measured distance by the change in motor positions:

   micrometers per step = (first distance − second distance) / (steps the motors moved)

With this value, the "Gap Between Arms Range" follows from the measured distance minus the part already covered by the two arms:

gap = (distance between the arms) − (left arm position + right arm position) × micrometers per step

The "Gap Threshold" is the minimum distance, in micrometers, that the arms and the membrane mounting brackets must keep between them during operation.

The "Left Membrane Bracket Size" and "Right Membrane Bracket Size" are each measured from the center of the bolt that mounts the bracket to the arm to its edge on the membrane side.

Firmware parameters

These are low-level constants that the firmware uses to build its motion profiles. They must match the firmware running on your device.

The "Firmware Linear Mode Speed Offset" and "Firmware Sinusoidal Mode Speed Offset" are both the minimum time between movements, expressed in the firmware's own time unit (which the "Firmware Time Base" can convert to microseconds). In linear mode the offset stays the same throughout the movement, while in sinusoidal mode it varies to shape a sine-like curve, so here the maximum value has to be used.

The "Firmware Time Base" and "Firmware Min Step Time" feed the time-shift calculation that determines the time between steps, and with it the speed of the movement.

All of these values exist to avoid overflows in the firmware's time calculations. Such an overflow can lead to incorrect motor positions, or freeze the device so that it needs to be reinitialized. The "Firmware Overflow Value" is the critical value at which such an overflow occurs.

Operating Mode

The "Operating Mode" determines how the application interacts with the stretcher device. In "Normal" mode the application connects to the physical device. In "Debug" mode the application runs without a physical device and executes all operations immediately. The "Mock" mode is like "Debug", but simulates all operations as closely as possible to the real behaviour.

Minimum Log Level

The "Minimum Log Level" controls how much detail is written to the log files, from most to least verbose: "Verbose", "Debug", "Information", "Warning", "Error" and "Fatal". A lower level records more, which is useful when diagnosing a problem.