(2002-) Helios VII, illustrated in Figure 1, consists of two crawlers independently actuated by motors m1,m2 and respectively connected to the main body by actuators m3 and m4. Thus tracks can be rotated 360degress relatively to the chassis. This feature can be utilized for stability control. The chassis acts as a base for an arm with four degrees of freedom supplied by the pair m3 and m4, and motors m5, m6, and m7.
M8 and m9 are utilized to actuate the simple gripper.
The arm is considered mainly to assist the motion of the vehicle, however it can be utilized also for grasping tasks. Four passive wheels to help the vehicle sliding over obstacles are installed on the shaft of the elbow and at the tip of the arm.
Fig.1 Helios VII
Table.1 Main Specifications of Helios VII
Arm (Extended)
1200[mm]
Track unit (width)
200[mm]
Track unit (height)
230[mm]
Speed
0.72[km/h]
Total mass
90[kg]
Control
Wifi
Fig.2 Concept of Helios VII
Tracks are wrapped around three main wheels: the front and rear sprockets with equal diameter, but smaller than the middle one. Because of the particular lateral shape of the treads, in steering motion, only a small area of the belt is in contact with the ground and low friction is generated. Main characteristic of HELIOS VII is the capability to control the vehicle center of gravity. In fact by changing configuration with the manipulator, several motion capabilities can be carried out.
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b
c
d
Fig.3 Helios VII stairs climbing
Stairs Climbing
As for the previous version HELIOS VI, HELIOS VII can climb over stairs by utilizing the manipulator and its passive wheels as shown in Figure 3-b.
Besides, in case of steep stairs, the arm can be utilized to maintain the center of gravity in the stable zone while climbing up as illustrated in Figure 3-a or in Figure 3-c,d.
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b
c
Fig.4 High step climbing motion
High Step Climbing Motion
Helios VII can overcome a high obstacle by using the manipulator as a lever. Figure 4, illustrates three images of the described motion. As shown in the figures, while crawling up the step, gripper is retreated between the passive wheels. In this way, fingers are protected and passive wheels firmly looked to obtain a stable supporting point on the ground (This mechanical feature is shown in Figure 5-b).
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b
Fig.5 Grasping operation and gripper control
Grasping Operations
HELIOS VII can lift heavy objects by utilizing its motor power (Figure 5). As shown in Figure 2, the gripper consists of a pair of worm screw sharing one fixed gear. Figure 5-b illustrates that by actuating according to the desired motion actuators m8 and m9, it is possible to change the grasping point and open or close the fingers.
Figure 6-a shows HELIOS VII raising its chassis by an inverse actuation of motors m3 and m4. In Figure 6-b the vehicle is represented in compact configuration.
System Architecture
New AC Motor drives are based on SuperHTM microprocessor SH7047, all of them are connected in chain by utilizing TitechWire bus technology. Two additional DC motors of 20W respectively controlled by a Titech SH2 Tiny and a pair of motor amplifiers are utilized to actuate the gripper. The TitechWire PC board is installed right under the chassis. By serial communication it communicates with the small TitechSH2Tiny controller to send the command for the gripper control. TitechWire PC runs under a Linux OS a server application that accepts TCP/IP WiFi connections. The power for the robot in this first prototype is supplied from an external source via cable.
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b
c
Fig.6 Helios VII experiments
References:
[1] M. Guarnieri, P.Debenest, T.Inoh, E.Fukushima, S.Hirose "Mechanical design and basic tests on Helios VII a vehicle for search and rescue operations". Journal of Advanced Robotics. Special Issue on Rescue Robotics. p.901-927, Vol.19, n.18, 2005
Terrain Adaptive Crawler Vehicle "HELIOS-VII"
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