motion system—
Basic chassis,electric componet LIJIAYUN(ZOE)
01
goals
1.Determine the appropriate distribution of electronic component locations.This will affect the total dead weight of the box, the total occupied space.
2.Calculate then select the right electronics.
3.Design of suitable mechanical structures and electronic circuits.Trying to be aesthetically pleasing and effective
goal one: Determine the appropriate distribution of electronic
For the electronics of this system, the centerpiece is the motor. The position of the motor will determine the center of the wheels and thus the center of gravity of the luggage compartment.After deciding on the location of the motor, other electronic components are integrated in its vicinity, except for special needs (e.g.,battery need easy disassembly and removal).
there are three viable options(As pic):
1.The first thing that can be considered is to fix the motor externally on the side of the box, by means of an aluminum profile.The advantage is that it has a low center of gravity, so it's a little more effortless.
2.Mount the motor inside the trunk and link the wheels by punching holes through the side
3.The third is an external chassis on the bottom of the trunk.
The first requires the installation of aluminum profiles on top of the bottom plate of the suitcase, which increases the weight of the suitcase and increases the width of the suitcase.
The second requires space inside the suitcase, and since the center section of the suitcase has a zipper for expansion, this installation will affect its expansion.
The third one would raise the geometric center of the suitcase, but it would require less weight to be added, would not affect the expansion, and would not take up the original space, so it was decided to go with the third one.
goal two: Calculate then select the right electronics.
(a) motor calculation
The motor mainly provides an auxiliary role for moving the luggage.
Assumption Luggage weight: 12kg
According to the data, the average walking speed of adults is Line speed 1.3m/s.
The diameter of the soft wheels used will change, the range is Wheel diameter: 340 to 370mm
Line speed required v = LineSpeed/πR = 1.3/(3.14*0.175)=2.36 m/s
Angular velocity w = v/0.175 = 13.49 rad/s
Assuming the required start-up acceleration is Acceleration: 1.3m/s^2
Friction coefficient(change in different materials ground): 0.15-0.5
Combined force in the direction of linear velocity required Combined force: = umg + ma (assuming the user is mostly providing the initial power) = 0.3*12*9.8 + ma= 35.28N
two motor provide total combined torque: = F*R = 35.28*0.175= 5.95N
so for one Motor: torque=3Nm , rpm 80
(b) control board, battery and motor driver selection
1.For dc motor, motor driver need to provide enough energy for it. Before we use L298N, which limit power is 25W. So, we choose other one driver basic on L298N however able to provide 160w power.
2.For control board, both esp32 and arduino uno could be use.
3.For the battery,this study will look for a battery that meets the requirements ofthe International Air Transport Association (IATA) [1], also removable and safe to use . The limit for most of contry allow to bring during airline is 75Wh, so we will pick a battery less than it.
4.Motion Control Switches is FSR402 pressure sensor. In according to realizate of a system that can control speed at will
goal three: Design of suitable mechanical structures
The design of the chassis is shown in Fig. The sides are reserved for possible extensions and the center is designed according to the selected control board and insofar as possible, without affecting the load-bearing capacity, while reducing weight.
reduce the length so will no effect the ex
Here is a holder for covering the electronics connecting the chessis.
Also, users can use the holder as a grabber when needing to transfer luggage to the rack
We use TPU95A to print the bttery holder, you can easily take it off and the battery wouldn't dropped from your lugguage.At the same time, the not-quite-enclosed space above provides you with the ability to check the remaining battery level at any time.
02 conclusions
