The SPEEDBOX can be configured to run a specific test based on a number of available start and end parameters, such as speed, hardware trigger, etc. In the documentation we refer to a test performed in this way as a "triggered test" regardless of whether it is activated/deactivated by a hardware trigger or by a virtual trigger, such as passing a speed threshold. During a triggered test various measurements from the test start location to the current position (during the test) or the test end condition (following the end of the test) are output. Details of the various parameters output during triggered testing can be found here. Additionally, the SPEEDBOX can be configured to output either or both analogue and/or pulse output only during a triggered test, in order that these outputs can be effectively "gated" to the period of interest defined by the test parameters.
Enable Triggered Testing
Tick this box to enable triggered testing using the parameters specified. Leave this box unticked to disable triggered testing. When unticked all of the other fields in this tab will have no effect.
Enter the name of the test here, this is the name that will be used to identify the test in text-based output. This field can be left blank if desired. The test name can be up to 16 characters long, valid characters are uppercase letters 'A' to 'Z', digits '0' to '9' and underscore '_'.
Start condition / End condition
Test start and/or end can be configured to be triggered by the speed passing either above or below the required speed threshold, which can be set in m/s, kph, mph or knots. In the example shown in the screenshot, the test is configured to start when the speed passes below 100kph, and to stop when the speed passes below 2kph. In order to "arm" the test, it is first necessary for the speed to pass above or below the trigger speed in the opposite polarity to that configured by a certain margin in order to avoid triggering on noise whilst passing the speed threshold in the wrong direction. This margin is currently set within the SPEEDBOX firmware at 0.8m/s (2.88kph). Thus in the example shown, it would be necessary to accelerate first to at least 102.88kph in order to arm the test. The test would then become active at the instance the speed hit 100kph whilst decreasing.
Pull away is only available as a start condition. It is used to enable acceleration tests that start from a halt. There are two options available: Pull away (acceleration-based) and Pull away (speed-based). Pull away (acceleration-based) starts timing when the inertial sensors detect movement. This is the most sensitive system, and will start timing as soon as the vehicle starts to move. This gives the most absolutely accurate results. Pull away (speed-based) starts timing when the system detects that the vehicle is moving based on speed detection. This is slightly less sensitive, but has the advantage of being consistent with measurement equipment from other manufacturers currently used within the automotive industry.
Halt is only available as an end condition. When enabled, the system will end the test when it detects that the vehicle has come to a halt.
Triggering based on either the longitudinal or lateral acceleration can be set to start above or below a set limit, in either g or m/s^2 dependent on the units set in the "Test units" field. Accelerometers is filtered to give a 20Hz bandwidth prior to evaluation by the triggering system.
Any of the four analogue inputs can be used for triggering starting or stopping of a test. The condition is set in terms of the input being above or below a target voltage value. Analogue channels are sampled at 200Hz, as a result there is a maximum of 5ms latency when used as a test trigger. No filtering is applied prior to trigger system evaluation; hence a clean voltage input is required.
A test can be started or stopped by a hardware trigger input, either a rising or falling edge. Typically this is likely to be supplied either by a pedal sensor or a laser barrier with detector. The trigger has an internal pull-up. Therefore it is in the "high level" state when no switch is physically connected. A switch which connects the inner and outer of the BNC connector together would cause a falling edge when the button is pressed.
A test can be started or stopped by a message received from a serial port from a DASH4PRO, one of the buttons on the DASH4PRO must be set up appropriately to send this command.
A test can be configured to end after a certain path distance has been covered, in either m or ft dependent on the units set in the "Test units" field. Distance is only available as an end condition.
The units for speed [m/s, mph, kph or knots], accleration [g or m/s^2] and distance [m or ft] can be set here. These are both the units in which the trigger conditions are specified, and the units in which any textual output will be output.
The configuration for MFDD (mean fully-developed deceleration) is specified here. MFDD thresholds can be specified either as a percentage of the start speed, or as fixed speeds using the currently configured speed units if the checkbox "Calculate MFDD at fixed speed thresholds" is checked. In either case, the MFDD will be flagged as invalid in the output if the configured MFDD thresholds cannot be physically passed by the configured test.
MFDD when using percentages is calculated as ((start_speed x (MFDD_start_threshold/100)) - (start_speed x (MFDD_end_threshold/100))) / (end_time - start_time)
MFDD when using fixed speeds is calculated as (MFDD_Start_Speed - MFDD_End_Speed) / (end_time - start_time)
Text output formatting
This section governs the formatting of the textual output generated by the SPEEDBOX during a triggered test. The textual output can be configured to contain no regular intervals (only a summary is output), regular speed intervals (test state every 10 speed units is output), or regular distance intervals (test state every 10 distance units is output). For regular speed intervals, path distance at each interval is automatically output. For regular distance intervals, speed at each interval is automatically output. Additionally, every line of test state output can optionally include Time into test, Deviation distance and/or Acceleration, as specified by the available checkboxes.
The triggered test can be set to activate the analogue outputs, the distance pulse output, or both. At a test boundary that is defined solely by a hardware trigger (i.e. Trigger rising or Trigger falling) the latency in starting the analogue and/or pulse output will be minimal, typically < 2ms. At a test boundary that is defined by including any other condition the latency in starting the analogue and/or pulse output will be increased significantly, and will typically be < 80ms.