What should the machine do if the wireless remote control signal is lost?
The machine must go to a safe state immediately and stop the motion. EN 13557 (controls and control stations on cranes) requires stopping on loss of signal in wireless control; in its annex it counts the stopping function of a wireless remote control as a safety-related control part and requires a category 3 or higher design. Other relevant standards are EN 60204-32:2008 and EN 13135:2013+A1:2018.
Loss of signal is an unavoidable operating condition of a wireless remote control: the battery runs out, the operator goes out of range, an obstacle gets in the way. The job of the design is not to prevent this but to behave predictably and safely when it happens.
The expected behaviour consists of these elements:
- Timeout: the receiver cuts the motion within a defined period after the flow of valid packets stops. On the HCT402, for example, this period is 250 ms; the motor goes to the safe centre position and oil flow stops.
- Safe default state: the outputs return to a de-energised or neutral position; no motion continues in the absence of signal.
- No automatic restart: when the connection returns, the machine must not move by itself; the operator has to give a deliberate command.
- Architecture: the stopping chain must be designed so that a single fault does not cause the function to be lost.
Verifying this in acceptance testing is easy: during motion, remove the remote control's battery or carry it out of range and observe whether the machine stops and whether it starts moving by itself when the connection returns. This test should be repeated at every commissioning.
Full topic: Wireless remote control installation: pairing, relay, safety