Robot manipulator and control method thereof

Robot Manipulator Control Technology Compensating for Nonlinear Friction Using a Low-Pass Filter Observer

This technology is a robot manipulator and control method that estimates and compensates for nonlinear friction in real-time without linearization. It utilizes only the robot's built-in motor current and encoder-based joint position data, eliminating the need for external force/torque or acceleration sensors by employing an observer equipped with a low-pass filter.

Conventional friction measurement methods often suffer from low cost-efficiency due to the requirement for expensive force/torque sensors, while observer-based methods frequently face issues with reduced estimation accuracy and limited application scope when simplifying nonlinear friction characteristics.

This technology proposes a method that mathematically estimates friction torque within the robot's dynamic equations using an observer with an integrated low-pass filter. It performs calculations while preserving nonlinearity, based on a dynamic model that includes the inertia matrix, Coriolis force, gravity vector, and gear ratio. By compensating for friction without additional sensors, it significantly improves positioning precision, making it ideal for precision assembly and force control tasks.

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Key Features:

• A sensing step that acquires joint information, including the rotation angle of the joint, and motor current.
• A step that estimates and calculates friction torque based on the sensed joint information, motor current, and pre-set estimation data.
• A configuration that estimates friction torque within dynamic equations via an observer with an integrated low-pass filter.
• A control step that compensates for friction by incorporating the estimated friction torque into feedback control.

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This invention was developed with support from the Ministry of Science, ICT and Future Planning for human-product haptic simulation technology.