A theoretical and experimental investigation of explicit force control strategies for manipulators

Abstract

This paper presents a complete overview of basic strategies that have been proposed for force control of robot manipulators. First, the model of the plant t o b e c o n trolled is reviewed. Next, the strategies are divided into force-based and position-based categories, according to previously reported implementations. Each of the controller types within these categories are analyzed, and predictions of stability and e cacy are made. Then it is shown that these two categories are actually the same, and this recognition leads to the concept of a novel second order low pass lter controller. Finally, all of the controllers are experimentally tested on the CMU DD Arm II , con rming the theoretical predictions. Among the important results presented is the conclusive demonstration for the rst time that integral gain control is the best basic strategy for force control of manipulators.

Force control and nonlinear master-slave force profile to manage an admittance type multi-fingered haptic user interface

“…Reference [7] also implemented active damping in the design as it provided a stabilizing effect and took advantage of some simplifications available due to its application on a fixed surface rather than a moving point. The results of the study showed that integral control generated the most effective performance.…”

“…The explicit force controller utilized in [8] also included the inertial term in addition to the terms compensated for by [7] and thus approximately compensating for all of the haptic device's dynamic effects, leaving control of just the force of interest. Issues associated with inappropriate approximations arise from this technique but appeared to be adequately compensated for by the integral term in its force PI controller.…”

“…The explicit force controller implemented by [7] utilizes a model based root locus approach in its comparison of various forms of conventional position, integral, and derivative force controllers. In order to achieve this end, the controller also utilizes active gravitational compensation as well as friction, Coriolis, and centripetal compensation in the development of its robotic arm model thus leaving the inertial terms for the controller gains to accommodate.…”

“…The admittance-type devices can be much more compact with the same strength capacities as that of impedance-type devices due to their geared or otherwise nonlinear strong actuators. However, these devices are difficult to backdrive and require force sensors as inputs to control the device's position/velocity (admittance control [5]), or force (force control [2][6] [7][8]). Although both structures have been implemented in HHUIs, each one has had to develop various methods for accounting for the associated shortcomings.…”

On Stiffness Regulators with Dissipative Injection for Robot Manipulators

“…Direct methods involve an explicit form representation of force-feedback, while in indirect methods force-feedback is not explicit but rather is regulated using the position of the end-effector. Among the most important direct interaction control approaches, we might consider explicit force control [5][6][7], hybrid force/ position control [8][9][10][11][12][13][14][15] and parallel force/motion control [16,17]. Meanwhile, among the most relevant indirect interaction control approaches, the stiffness control [18][19][20][21][22] and impedance control approaches [2, 4, 23 -29] might be considered.…”