Page 30 - Electric Drives and Electromechanical Systems

22 Electric Drives and Electromechanical Systems

actuation. Irrespective of the detailed design of the individual fingers, they are required
to be mounted on a supporting structure, this is more fully discussed in academic papers
such as Pons et al. (1999).

1.3.3 Mobile and swarm robotics
In recent years there has been a considerable increase in the types and capabilities of
mobile robots, and in general three classes can be identified: UAV (unmanned aerial
vehicles), UGV (unmanned ground vehicles) and UUV (unmanned underwater vehicles).
In certain cases, the design and control theory for a mobile robot has drawn heavily on
biological systems, leading to a further class, biologically inspired robotics and swarm
robots. An early example of this type of robot was the Machina Speculatrix developed by
W. Grey Walter (Holland, 2003), which captured several principles including simplicity,
exploration, attraction, aversion and discernment. Since this original work a consider-
able number of robots have been developed including both wheeled and legged. The
applications for mobile robots are wide-ranging and include:
Manufacturing systems. Mobile robots are widely used to move material around
factories. The mobile robot is guided through the factory using underfloor wiring
or visual guidelines. In most systems the robots follow a fixed path under the con-
trol of the plant’s controller, hence they can move product as required by the
manufacturing process.
Security systems. The use of a mobile robot is considered to be a cost-effective
approach to patrolling large warehouses or other buildings. Equipped with sensors
they are able to detect intruders and fires.
Ordinance and explosive disposal. Large numbers of mobile robots have been
developed to assist with searching and disposal of explosives, one example being
the British Army’s Wheelbarrow robots. The goal of these robots is to allow the in-
spection and destruction of a suspect device from a distance without risking the
life of a bomb disposal officer.
Planetary exploration. Fig. 1.11 shows an artist’s impression of one of the two Mars
rovers that were landed during January 2004. Spirit and Opportunity have consider-
ably exceeded their primary objective of exploring Mars for 90 days, with Spirit
operated for over 2000 martian days and driven over 7.7 km and Opportunity
operated for over 5000 martian days before being engulfed in a global martian
dust storm. In that time Opportunity has driven over 45 km and returned over
220,000 images to earth. It should be noted that each rover incorporated 39 d.c.
brushed ironless rotor motors (see Section 5.2), used to drive the wheels, robotic
arm and camera positioning. These motors were of standard designs with a num-
ber of minor variations, particularly as the motors must endure extreme condi-

tions, such as variations in temperature which can range from -120 Cto þ25 C.