Research-Converting Power into Movement

Assuming that the mechanical insect will be powered by some sort of motor research needs to be undertaken to determine how the power generated from the motor can be converted into movement. This section will look at possible ways of achieving this focusing on individual components and the part they will play in achieving movement.

 

Using a geared motor attached to a wheel would be one way of producing movement. The pictures on the left detail two individual motors attached to wheels, both powered by there own set of batteries. With each wheel being powered independently it gives the user the option to power each independently, for turning, or together for forward/backward movement.

Clearly, with the way that insects/creatures move this arrangement may not be suitable for my type of project. However the wheels could easily be replaced with other components. The important point within this arrangement is the geared motor allowing control over the eventual movement created.

NB: To reduce the speed of the motor a HIGH ratio needs to be selected, for example 120:1

  

Another option is to use a standard motor with an exposed splined drive shaft. This allows a system of gears to be added, tested and modified easily. This scenario is ideal if the required gear ratio is not known as the gears can be changed until the right speed is achieved, see above.

Cams are a common way of converting rotary motion to linear motion. Most commonly seen in engines, cams are used to take the rotary motion of the rotating shaft provided by the motor/engine and turn it into a linear motion to open and close the fuel intake and exhaust valves which are operate in an up and down movement. See fig 1.  

Fig 1: Nissan’s ‘Variable Valve Event & Lift’ technology developed for

 the Infiniti G37 coupe

Fig 2 illustrates  a cam works in a very simple and clear system. The eccentric shaped cam means that as it rotates around the shaft it will come into contact and move part ‘x’ in the direction of the arrow.

There are also different types of cams. The eccentric shaped cam pictured on the left is an example of a plate cam, as stated above this moves another part (called the follower) when the shaft rotates. By altering the shape of the cam we can alter the output produced, for example a notched shaped cam could be used to trigger a switch at various intervals.

 

 

The music box on the left is another example of a cam offering a different type of output, both movement and sound. The drum which has numerous high spots is driven in a rotary motion by a drive shaft attached to a wind up motor. The high spots hit the fingers forcing them upwards in a linear motion creating the note.

 

Worm Gears are also a useful way of transferring power from the motor to other moving parts. Fig 4 illustrates how a worm gear can turn rotary motion occurring on one axis into rotary motion on a different axis.

The motor could be attached to either the cog or the shaft of the worm gear depending on where the power is being transferred to.

Fig 4 

Servomechanisms, or servo’s for short are a small device with a small output shaft that is driven by a motor. The output shaft can be positioned to specific angles via coded singles that are sent from a chip. The servo can maintain this angle or keep moving to various angles depending on the signals being sent.

Connected to the output shaft is a potentiometer, this allows the circuitry to monitor what angle the shaft is at and when the programmed angle is achieved the motor switches off.

 

Servo’s are normally capable of travelling  between 0 and 180 degrees, but this varies between manufacturers. If the distance the shaft has to move is large, the motor will run at full speed, but if the distance is small the motor will run slowly. This is called proportional control.