42 CHAPTER 1 / SENSOR-BASED PLANNING AND CONTROL FOR ROBOTIC SYSTEMS
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FIGURE 1.23
Compensation of unknown load by force-torque feedback.
In Figure 1.23, two different boxes, weighing 0.45kg and 1.8 kg, were lifted by the
dual-arm system without force feedback in their controllers. It is shown that an increase of
the load significantly reduces the accuracy of the coordination. However, if force feedback is
used, as shown in Figure 1.23, the effect of increased load on the coordination is very small.
That is, without knowing the change of load, the use of the force feedback in the nonlinear
feedback control law (1.52) can automatically compensate for the unknown load. Therefore,
high-accuracy force measurement and feedback play important roles in a multirobot system
coordinated control.
These experimental results demonstrate the advantages of the event-based coordination
scheme. The significance of the event-based coordination scheme is that it can handle some
unexpected events, and the control is carried out on the task level. Furthermore, the structure
of the control system is task independent. It makes it possible for the multirobot system to
work on complex tasks. Therefore, the event-based coordination scheme can be an important
step toward the development of intelligent multirobot systems.
5 IMPLEMENTATION OF EVENT-BASED PLANNING AND CONTROL
5.1 Introduction
The practical implementation of the planning and control scheme is an important step in the
development of robotic systems. It consists of two issues. First, one is developing a planning
and control scheme that can be easily and efficiently implemented. The second issue is
developing an efficient and user-friendly computing architecture for the implementation.

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