Forcelimiting

Forcelimiting is the practice of constraining the maximum forces that a system can exert or experience. It is used to protect components from overload, prevent unintended motion from causing damage, and reduce the risk of injury to humans or delicate materials. Forcelimiting can be implemented through passive hardware, active control, or a combination of both.

Passive force-limiting devices rely on physical properties and simple mechanisms that restrict force without requiring sensing or computation. Examples include mechanical stops that halt movement at a defined position, shear pins or slip clutches that disengage at a threshold, torque limiters, and energy-absorbing interfaces or compliant joints. These elements dissipate or absorb excess energy, often with predictable, one-time or limited-life performance.

Active force-limiting uses sensors, actuators, and control algorithms to monitor forces and reduce or redirect input to the system. Techniques include impedance or force control, where actuator commands emulate a compliant interaction, and fast feedback loops that keep contact forces below programmed limits. In safety-critical applications, control logic may enforce hard limits or introduce safe shutdowns when thresholds are exceeded. Implementation requires reliable sensing, low latency, and robust fault handling.

Common domains include industrial and collaborative robotics, surgical and rehabilitation devices, prosthetics, aerospace mechanisms, and automotive safety systems. Force-limiting helps enable gentle manipulation of objects, protects tooling from overload, and mitigates collision forces in automated environments.

Designers must consider sensing accuracy, latency, hysteresis, repeatability, and fault tolerance. Calibration and testing against standardized limits are essential. Relevant standards address machine safety, such as general machinery directives and robot safety standards, and may specify verification of force limits and response times.

See also: force control, safety engineering, torque limiting, impedance control.