Wireless Controlled Pneumatically Operated Wall Climbing Robot – Mechanical Project
How to make wall climbing robot
A wall climbing robot is a robot with the capability of climbing in vertical as well as horizontal direction with efficient attachment and detachment. The bot is designed to replace the activities carried out along the wall at high heights which would risk the human life. This paper describes the fabrication of a pneumatically operated
wall climbing bot which uses suction cups as a mean of sticking to the wall. Each vacuum generator will operate two suction cups on either vertical or horizontal limb of robot. Linear movements are achieved through double acting pneumatic cylinders. A wireless communication link can be interfaced to the electric circuit of solenoid operated DCV’s making bot operation semi-autonomous and autonomous also. The bot is adaptable to various wall materials such as metal, ceramic, glass, concrete, wood. Currently the robot is designed only for linear movement. Further scope of development in this prototype includes imparting other locomotion capabilities such as turning movements, angular movements shifting bot from one plane to another thus, making it omnidirectional.
Wall climbing bots are special mobile robots that can be used in a variety of application like inspection and maintenance of surfaces of sea vessels, oil tanks, glass slabs of high rise building etc. To increase the operational efficiency and to protect human health and safety in hazardous task make the wall climbing robot a useful device.
Robots have been created to assist or replace humans in various dangerous and difficult tasks. Robots have been used in construction, manufacturing, security etc. This is because they are able to adapt to different environment conditions and situations. They have conquered nearly all environments that humans have put them through. Climbing robots can be used on artificial surfaces like a wall, or on natural surfaces like trees or cave walls. They are desirable for several applications such as search and rescue.
Pneumatic adhesion :
This is the another technique also called as negative pressure adhesion which can be distinguished between three different types: passive suction cups, active suction chambers and vortex or thrust systems. Passive suction cups are suitable only on very flat surfaces like glass but can be combined with different types of locomotion like Tracked Racoon or the Dexter robot having two articulated fits. In active suction chambers, suction cups are used along with electrical vacuum generators which produces a large through flow volume or high negative pressure. They can be used on rough ground in comparison with passive cups as they produces high attraction forces and can be combined with nearly every locomotion system e.g. WallWalker , Bitclimber, LARVA.
In literature various combinations exist combining different types of locomotion with different adhesion principles. During robot development a question has to be considered: What kind of locomotion principle is the optimum for the given task and the environment. In general, one can distinguish three classes of locomotion with their individual assets and drawbacks:
1. Arms and Legs : This locomotion principle resembles the movement of lizard on a wall which includes alternate forward movement of one of the arms or legs and by pivoting the other at the same time. The main advantage of this locomotion principle is that the robot is highly adaptable to wall surface structure which includes overcoming obstacles, small steps, etc and translation of robot from ground to wall. However, high degree of freedom leads to complicated mechanical structure and control system which ultimately results in higher weights, larger torques and slow movement.
2. Wheels and Chains : Wheeled or tracked locomotion is the fast and continuous movement and the simplest mechanism to employ. Magnetic or pneumatic adhesion system can be used in combination with this locomotion system, but it has a limitation of lifting load capacity since the power input of motors driving the wheels is insufficient at high carrying load. Also, motors of wheels must be mounted on robot which results in increase in dead load of robot.
3. Pneumatic actuators : Pneumatic actuators with sliding frame are very commonly used locomotive principle. The main purpose of using this system is that it provides wide range of lifting load capacity from 0.25 kg to 100 kg on varying the supply pressure of compressed air. Regulation of air flow rate to actuators enables us a great control on climbing velocity in case of precise motion applications. The drawbacks of this principle are again a low speed compared to wheeled or tracked vehicles, a discontinuous movement due to the stick-move-stick-move cycle. By considering precision and payload capacity, pneumatic actuators with sliding frame is selected as locomotive principle for wall climbing robot.
Assembly of both limbs of robot i.e. vertical and horizontal limb is done separately. It begins with insertion of both threaded ends of cylinders in 22 mm drill of L-plate and tighten it firmly with the help of locknuts. Piston rod end is fixed to center drill of teflon piece. Then, sliding rods are inserted in 7 mm drills of teflon piece through which it can slide freely. Rear ends of sliding rods are fixed rigidly in 7 mm drilled holes of L-plate
mounted on piston rod side of cylinder. Front ends of sliding rod are fixed to the L-plate on opposite end as shown in fig. In this way, assembly of one limb is complete.
Similarly, other limb is assembled and Teflon pieces of both limbs are kept over each other. Both limbs are fixed to each other permanently by inserting blue rod through teflon pieces as shown.
Pneumatically operated wall climbing bot mainly composed of two limbs:
i) Vertical limb with cylinder 1 , suction cups S1 & S2 mounted on it.
ii) Horizontal limb with cylinder 2 , suction cups S3 & S4 mounted on it.
Double acting cylinder 1 and cylinder 2 are used for motion along X-axis and Y-axis respectively. Both cylinders are actuated through solenoid operated spring return 5/2 direction control valves. When control unit sends electric pilot signal of 12 V to any DCV coil, spool position is shifted resulting into extension stroke of cylinder.
Flow control valve is inserted in path to regulate the extension velocity of cylinder. Vacuum generator is a small device which creates vacuum pressure to outlet port when compressed air passes through its orifice. Suction cups S1, S2 are operated through vacuum generator VG1 and S3, S4 are operated through VG2. Both VG1 and VG2 are provided with compressed air supply through solenoid actua ted spring return
3/2 direction control valves. Pneumatic hoses, T-connectors, inline connectors are used for all pneumatic connections.
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