Vertigo Event Tutorial

Clasping Mechanism- For the bot to move on the zip-line (which is basically a metal rod of square cross-section) , it should physically clamp onto the metal bar. Thus, there arises a need of a clasping mechanism. There are different ways in which the bot can clasp onto the zip-line. One of the mechanisms that can be used here is a simple mechanical arm. The bot clasps onto the zip-line using an assembly that resembles a human hand with an arrangement of wheels along the sides of the metal bar.The arrangement of wheels in a mechanical arm can be of different types.Two of such arrangements are shown below-

The upper wheel supports the weight of the bot and the side wheels regulate the movement of the bot  from the sides, not letting it topple to one side.
Images showing the above mechanism are displayed below-

Locomotion- For the bot to move on the zip-line, it requires a mechanism that enables it to move on its own. Here arises the need of a locomotion system.The locomotion of the bot basically includes two other mechanisms-

• Driving Mechanism
• Braking Mechanism

1. Driving Mechanism- The bot propels forward using electric geared motors.These motors can be attached to the wheels in several ways. One such arrangement is shown below.
   

For moving your bot on the zip-line, one essential factor that comes into play is FRICTION. If there is not sufficient friction between the wheels and the zip-line, the wheels will actually slip resulting in poor control over the bot. However, if the friction is too much, it would be tougher for the driving motors to move the bot. To solve this problem, we go to the basic roller-coaster science. Below is an image displaying a roller coaster wheel:


Thus, the steel rim provides sufficient strength to bear the load while the polyurethane layer over it provides sufficient grip and friction for easy movement.
Propelling the bot can we done in yet another way. Using air can be another mode to drive the bot. Mechanical rotors run by electric motors that push back air is the basis behind this mechanism.

Braking Mechanism- This is a small but a major requirement of the bot. Braking is necessary to regulate the movement of the bot. It can be achieved in different ways either through a simple cycle type braking mechanism or electromagnetism. To start with,a simple cycle type braking mechanism is explained below.


Working-
1.This mechanism involves stopping the rotating wheels by bringing them in contact with a rubber stopper.
2.The extent of braking is regulated by a hand held lever.
3.The springs help to bring back the stoppers at the original position once the brakes are released.

There can be many different ways to brake the motion of your bot. One such way is the eddy-current brakes or the electromagnetic brakes-

Working-
1.In this mechanism, a non-ferromagnetic metal disc (rotors)is connected to a rotating coil, and a magnetic field between the rotor and the coil creates a resistance.
2.When electromagnets are used, control over the braking action is made possible by varying the strength of the magnetic field. A braking force is possible when electric current is passed through the electromagnets.
3.The movement of the metal through the magnetic field of the electromagnets creates eddy currents in the discs.
4.These eddy currents generate an opposing magnetic field, which then resists the rotation of the discs, providing braking force. The net result is to convert the motion of the rotors into heat in the rotors.

Images depicting the above are displayed below-

Storage- Storage is crucial for a bot swinging in air as it has to be ensured that the weight may not unbalance the bot. To overcome this, the balls can be stored in a spirally-shaped tube along the boundary of the storing container. This ensures that the weight remains uniformly distributed through out the body of the bot and the bot remains balanced-




However, a simple container can also be used to hold the balls, ensuring that the mass weight remains balanced and the bot does not get imbalanced.

Dropping mechanism- The dropping mechanism has to be as such that it enables us to control the number of balls to be dropped. For the requirement of the event, it should be one by one drop mechanism. Thus, in simple words the mechanism can be similar to a simple water tap mechanism where u can regulate the flow to each drop, in this case each ball.
A dropping mechanism can be designed using different mechanical or electromagnetic ways. A simple one by one drop mechanism is explained below-


Another kind of a simple dropping mechanism is shown below. It consists of a high torque motor that rotates a disk with cavities, containing balls. The balls rotate and fall one-by-one at the point where the lower base has been cut to let the balls fall. In order to make this a single drop mechanism, the controller has to be efficient enough with the time duration, the motor is run for, or even a lock mechanism using another small motor can be designed to restrict the motion of the disk.
Images of the same are shown below:




So by now, a clasping, braking, storage and a dropping mechanism is embedded to out bot and is ready for the first round. Our tentative bot looks as shown below-

Problem statement for the second round states that-
The bot has to move from a point A to the point B, changing zip-lines in between.

Thus there arises the need of the following additional  mechanisms-

1. Switching
2. Re-clasping
3. Differential Drive

Differential Drive-In the second round, the bot needs to detach itself off a zip-line and then re-clasp on the zip-line running parallel at a gap. The best way to traverse the gap between the two zip-lines is by using a Differential Drive embedded to our bot. For the working and making of a differential drive refer to


http://www.youtube.com/watch?v=kFoGBIqIqoM


A diagram to show working of a differential drive(DD)



Our bot embedded with a DD looks as follows:

Re-clasping mechanism by opening mechanism:A simple way to free the bot off the zip-line is by freeing it when it reaches the platform. If one side of the bot opens up, the bot gets freed, and can be moved and replaced easily with the help of the Differential Drive below. A simple construction and working of the above mechanism is shown in the figure below



After the bot opens up, it is taken away from the zip-line and re-clasped on the second zip-line using series of steps as shown below.

Re-clasping mechanism using Wrench mechanism (pinion gear):Another way to open up the bot, is by using a pinion gear mechanism same as that in a wrench but here driven by an electric motor. The construction of a simple wrench is explained in the images below.












The working of a wrench is shown in the following video-
http://www.youtube.com/watch?v=7jeEsWHQdqc

However, for the event, the wrench has to operate itself and this can be achieved by use of a motor at the pivot.This is shown in the following figure-


How the above works?




However, the the above mechanism can be simplified even more by a simple change in the type of wheel we use. You must have observed a rail wheel. It looks as shown below-

In the above pics we observe a common rail wheel, with one side of the wheel having a larger width than the normal width of the wheel. This extension helps a rail wheel to turn and prevents it from derailing giving support from sides. This similar mechanism can be used in out bot too, in a manner shown below

Using the top wheel as a rail type wheel and using suitable counterweights such that the bot remains balanced and does not lean to one side, will rule out the use of one side wheel resulting in the bot becoming lighter, compact and giving better control. The wheel on the right and proper balancing, prevents the bot from falling to he left and the top wheel supports both the weight of the bot and the motion from the side.

Tentative view of the same and its working is shown below-

Working is same as that of the wrench mechanism

In the second figure. the motor rotates and pushes the assembly upwards, as a result the upper wheel rises up, and the bot gets free from the zip-line. Now the bot is free to be driven on the platform, by the differential drive below, and can be re-positioned below the second zip-line and re-clasp and move further.

Yet another mechanism for switching and re-clasping can be achieved through a motor-belt mechanism.

Switching- For the bot to switch between zip-lines, it has to either extend itself and place itself on the other or simply detach itself from the first zip-line and re-position itself on the other.
A simple ‘spring -clip’ self clamping mechanism is shown below-



How does the above mechanism work?
1.The two pins A and B are brought together by bringing the arms close to which they are attached, by use of motors.
2. The pin B is such that it grazes the surface of the pin C when they are brought close. After a certain point, the bend of pin B gets struck in the bend of pin C as a result of which the system or the two arms of the frame are held together.
3. In the process of bringing them close the, the spring A compresses and tries to prevent the two arms meet. However, the forces bringing the arms closer are exerting a force greater than that exerted by the spring A.
4.Thus the system gets held together firmly, with pin B hooked in pin C.

How the above mechanism opens up?
1. The pin C has a wire attached, that pulls it downwards. The wire is same as that of the brakes in a simple cycle brake.
2. As soon as the taught wire attached to pin C is pulled downwards, the pin C moves down and the pin B is released.
3.The spring A expands and pushes the two arms apart. As a result the system opens up.
4.The spring below re-positions the pin C as soon as the wire is released, making it ready for further clasping.

Electromagnetic mechanism-The two arms of the bot can also be held together with an electromagnetic. One arm has a strong electromagnet at its end while the other has a ferromagnetic piece at it end. The attraction of the electromagnet keeps the arms held together.


How to regulate the angle by which the arms open up?
There are two ways to regulate the movement of arms-
1.Belt-Motor Mechanism- The arms are connected to a motor through a belt mechanism that regulates the opening and closing of the arms according to the requirement.

2. Pinion Gear Mechanism- The movement of arms is regulated by a motor and a pinion gear mechanism.
the working of the pinion mechanism is shown ib the following vid-
https://www.youtube.com/watch?v=wtN2py3KCG4&feature=related
http://www.youtube.com/watch?v=HMQ4u9UlPSQ&NR=1


In order to allow the bot to open up but still remain attached, we provide the bot with door hinges and attach the storage below using free rotation joints. this allows the bot to detach itself from the zip-line along but the position of the storage below remaining constant.

A diagram of the same is shown below-
To have a self clamping mechanism as explained above, we need to have a platform with motors and belt system or the pinion gear mechanism attached. The position of this platform should remain constant even when the bot opens up.
The best way to overcome this problem is by using a double door hinge along with movable joints. This is shown in the diagram below-

 

Above figure shows motors with belts fixed in the center of a double door hinge.

How does the above help us?
The fixed part of the hinge provides a compact and stable platform for fixing the motors for the self-clasping mechanism as shown below-

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