Dynamic Tensegrity Based Cooperative Control of Uninhabited Vehicles - Intelligent Computing for Sustainable Energy and Environment - page 490

It is well known that a large system can be easily managed by forming the sub-
systems with lower dimensionality within the complex system. Hence, the individual
subsystems can be analysed and solved efficiently [YNIL12]. Here, each subsystem
is formed by a follower vehicle (represented by the node) and a virtual leader (rep-
resented by cross bars' point, O ) with an interspacing distance of l b / 2 (half the bar's
length). Since all the vehicles are referring to the same virtual leader, a centralised for-
mation control method is implemented in the system that consisting of n subsystems,
where n is also represent the number of vehicles in the formation. Note that four such
subsystems are needed in the setup of the complete formation so that the modelling of
cross-tensegrity structure can be applied in the formation control.
For each subsystem in the formation, an individual tendon controller is designed
to synchronise a pair of vehicles according to the virtual leader as shown in Figure
2a. A direct communication link is established between the two vehicles whereas the
controller output is the tendon force which will be elaborated more in the following
section. The signal measured by the controller is the relative distance between the two
synchronised vehicles which is denoted by r ij . The position of a vehicle in the formation
is then controlled by the applied tendon force with respect to its designated neighbour
vehicle by specifying their equilibrium interspacing distance, l tensegrity . The position of
the virtual leader is used by all the vehicles in the formation to calculate the current
interspacing which the autopilot is required to regulate during the manoeuvring task.

Respo n ses of t h e Contr o l Param a ters

3

2

1

0

100 200 300 400 500 600 700 800 900 1000

l tensegrity 80

UV 2

f 12

UV 1

60

40

ș BS1

20

100 200 300 400 500 600 700 800 900 1000

l b1 /2

35

l b2 /2

30

25

20

Virtual Leader (O)

15

100 200 300 400 500 600 700 800 900 1000

Time (s)

(a) Relative control parameters in
a subsystem

(b) Control Parameters Responses

Fig. 2. Different Shape Transformation

θ BS are the two key control
parameters in estimating the vehicles' equilibrium distance ( l tensegrity ). For example,
UV 1 makes its decision to move according to the tendon force, f 12 that is applied on it
with respect to its neighbour, UV 2 in order to maintain their equilibrium interspacing
distance, l tensegrity . This tendon force is dependent on the relative distance between the
nominated pair of vehicles, r ij .
Hence, by varying the ratio of l b 2 / l b 1 , the bar-string angle (

The ratio of bars' lengths, l b 2 / l b 1 and the bar-string angle,

θ BS 1 ) changes and the
new equilibrium interspacing distance ( l tensegrity ) between the controlled vehicles can
be obtained as well. Figure 2b shows the response of the interspacing distance between
UV 1 and UV 2 changes according to the two key control parameters, l b 2 / l b 1 and θ BS 1 .