What is the purpose of a watchdog timer within a robot controller?

The purpose of a watchdog timer within a robot controller is to provide a safety mechanism that detects and recovers from software failures or system crashes that could cause the robot to behave unpredictably. A watchdog timer is essentially a hardware or software timer that must be periodically reset by the robot's main control program. If the control program fails to reset the timer within a specified time interval, the watchdog timer assumes that the program has become stuck or has crashed. In response, the watchdog timer triggers a predefined action, typically a system reset or a controlled shutdown of the robot. This ensures that the robot does not continue to operate in an erroneous state, which could lead to damage to the robot, the surrounding equipment, or even injuries to personnel. For example, if a software bug causes the robot's motion planning algorithm to enter an infinite loop, the watchdog timer would detect that the program is no longer responding and initiate a reset, bringing the robot to a safe, known state. Without a watchdog timer, such a software failure could cause the robot to continue moving uncontrollably, potentially leading to a collision or other hazardous situation. The watchdog timer acts as an independent safeguard, ensuring that the robot's behavior remains predictable and safe even in the event of software errors.