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### Author Topic: Robot Energy Tutorial  (Read 2298 times)

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#### Dont_Taz_Me_Bro

• Jr. Member
• Posts: 19
##### Robot Energy Tutorial
« on: October 02, 2009, 01:10:47 AM »
I was reading through the robot energy tutorial and the final energy equation is:

Required_Energy
= 2 * Kinetic_Energy
+ Potential_Energy
+ Energy_Losses
+ Conversion_Losses

Can somebody explain to me why you would multiply the kinetic energy by 2? Why does your battery need energy to stop the robot? Just turn off the motors and let friction do the rest....right? What am I missing here?

Here is the link to the tutorial...http://www.societyofrobots.com/mechanics_energy.shtml

In fact, let's say the destination is at the end of an incline. Couldn't you just assume the energy needed is the potential energy with additional amount after you factor in friction loss and other energy losses? Why would you include both the potential and the kinetic energy?

« Last Edit: October 02, 2009, 01:18:10 AM by Dont_Taz_Me_Bro »

• Supreme Robot
• Posts: 11,670
##### Re: Robot Energy Tutorial
« Reply #1 on: October 02, 2009, 08:57:11 AM »
Quote
Why does your battery need energy to stop the robot? Just turn off the motors and let friction do the rest....right? What am I missing here?
Friction? That means you need enough energy to overcome that friction just to start the robot. And coasting is not the same as stopping - especially if there is a wall in the way or your bot is rolling down a ramp

But you are right, coasting is more efficient than reversing the motors for a full stop. But try stopping at a red light without using your car breaks - there are many reasons why that is a bad idea.

Quote
Why would you include both the potential and the kinetic energy?
A robot goes up a ramp . . . the energy required is different if the robot stops at the top of the ramp, or if it keeps its velocity constant.

Calculating energy consumption is really tricky, and the most accurate way is through experimentation. But before you build your robot, doing the math will get you ball-park values to help you avoid massive redesigns from subjective intuition failures.

#### Dont_Taz_Me_Bro

• Jr. Member
• Posts: 19
##### Re: Robot Energy Tutorial
« Reply #2 on: October 03, 2009, 12:45:45 PM »
Let's say you are using servo motors....

If you turn off the power, will your robot just skid for a little depending on how heavy it is? Will it essentially stop if you have a slow velocity? Batteries have nothing to do with this instance right? To overcome that initial friction is that why you are multiplying the KE by 2? Just to be safe?

And I understand what you are saying about having a velocity at the top of the ramp.

I think a better equation would be....

Potential Energy Initial + Kinetic Energy Initial = Potential Energy Final + Kinetic Energy Final

• Supreme Robot
• Posts: 11,670
##### Re: Robot Energy Tutorial
« Reply #3 on: October 03, 2009, 01:08:23 PM »
Its KE x 2 if you want your robot to stop, or just KE to let your robot move infinitely (assuming zero friction).

Your confused as to where the energy is coming from. It requires KE x 2 to stop whether the energy comes from friction or the battery.

If your robot has high friction, meaning it'll stop as soon as you turn off the servos, that means you need much more than just KE and PE - you need to continually supply energy to counter the friction at all times.