APPLICATION DESIGN ISSUES - Hard Real-Time Computing Systems: Predictable Scheduling Algorithms and Applications - page 405

It is worth observing that this result can also be used to evaluate how long we can look
away from the road while driving at a certain speed and visibility. For example, if D
= 50 m (visibility under fog conditions), μ f = 0.5, Δ t = 300 ms (our typical reaction
time), and v = 60 km/h (about 16.67 m/s or 37 mi/h), we can look away from the road
for no more than one second!

11.2.2 ROBOT DEBURRING

Consider a robot arm that has to polish an object surface with a grinding tool mounted
on its wrist, as shown in Figure 11.7. This task can be specified as follows:

Slide the grinding tool on the object surface with a constant speed v , while
exerting a constant normal force F that must not exceed a maximum value
equal to F max .

camera

robot

force
sensor

tool

object to debur

Figure 11.7 Example of a robot deburring workstation.

In order to maintain a constant contact force against the object surface, the robot must
be equipped with a force sensor, mounted between the wrist flange and the grinding
tool. Moreover, to keep the normal force within the specified maximum value, the
force sensor must be acquired periodically at a constant rate, which has to be deter-
mined based on the characteristics of the environment and the task requirements. At
each cycle, the robot trajectory is corrected based on the current force readings.

As illustrated in Figure 11.8, if T is the period of the control process and v is the robot
horizontal speed, the space covered by the robot end-effector within each period is
L T

= vT . If an impact due to a contour variation occurs just after the force sensor has