  In this paper, an adaptive nonlinear strategy for the motion and force
control of flexible manipulators is proposed. The approach provides robust
motion control until contact is detected when force control is then
available--without any control switch--, and vice versa. This self-tuning in
mixed contact/non-contact scenarios is possible thanks to the unified
formulation of force and motion control, including an integral transpose-based
inverse kinematics and adaptive-update laws for the flexible manipulator link
and contact stiffnesses. Global boundedness of all signals and asymptotic
stability of force and position are guaranteed through Lyapunov analysis. The
control strategy and its implementation has been validated using a low-cost
basic microcontroller and a manipulator with 3 flexible joints and 4 actuators.
Complete experimental results are provided in a realistic mixed contact
scenario, demonstrating very-low computational demand with inexpensive force
sensors.
