Segways explained
Hey friends, Happy Wednesday!
Answer to the question I posed last week
Last week we discussed Segways and had asked how the turning mechanism works in a Segway? We’ll be exploring the same this week and conclude the discussion on this topic, this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for your food, etc. Let's jump in!
Tweet of the week
I’m sharing a cool fact about gadgets every day on Twitter. And here is one of them for you.
How do Segways turn while maintaining balance?
If you want to learn or revisit how Segways auto-balance, please check last week’s Newsletter issue here
The user uses the handlebar of the Segway to perform a turn. Pushing the handlebar to the right makes the Segway take a right turn. Likewise, for the left turn.
Figure: Performing a turn in a Segway (Source: Segway manual)
1. Stability: When you are making a right turn in your car, you get pushed towards the left due to centrifugal force. This is advantageous in the case of a Segway, as we lean towards the right for a right turn and the centrifugal pushes us to the left, giving us stability from not falling.
2. The more the angle of the handlebar, the more aggressive the turn (shorter radius). One can also turn in place by leaning accordingly.
3. But how does leaning convert into a turn?
Segway has a sensor (load cell) mounted close to the pivot of the handlebar at the bottom. A load cell is a sensor that basically converts a force such as tension, or compression into an electrical signal. As the force applied to the load cell increases, the electrical signal changes proportionally based on the PID algorithm - which implies a more aggressive turn. Hence, the more you push the handlebar to the right, the more the electrical signal, the sharper the right turn.
4. We need to command the motor with a balancing Torque to auto-stabilize the vehicle from not falling. But now, we need to apply a Yaw command as well, for performing the turn. How do we combine both? (Perform a turn while also maintaining stability and not falling)
Based on the direction of the handlebar motion, the left and right wheels are commanded as follows - Let’s take the example of a right turn.
MotorCmdLeft = BalanceCmd + YawCmd
MotorCmdRight = BalanceCmd - YawCmd
5. Here, each command is basically a voltage given to the left and right motor amplifiers.
BalanceCmd is the command sent by the controller to each motor amplifier to maintain the Segway in a balanced state while moving or at rest.
YawCmd is based on load sensor reading with direction. In this case, it increases the command to the left wheel, while decreasing the command to the right wheel. Thereby causing the Segway to execute a right turn.
6. Note that the left wheel has to rotate faster than the right wheel to make a right turn. Which is exactly what we’re doing here!
Blog posts
My blog post S4E6 exploring Segways is out! It has additional sections which we haven't explored in the Newsletter issues. Read it here, happy learning!
By replying to this email, let me know if you’d like to read about a specific gadget/device. And I can write about it.
Gadget of the week
Accessible makeup: L’Oreal presented a gadget called HAPTA, which is a handheld ultra-precise smart makeup applicator designed for people with limited hand and arm mobility so they can steadily apply lipstick at home. The smart motion controls plus customizable attachments give the user an improved range of motion.
Thank you for reading!
Have a nice rest of the week, and take care!
Until next Wednesday,
Chendur
