1. Crane Tether Mechanism
Cole Perrault
Spring 2016
ET 493
Dr. Cris Koutsougeras

3. Problem
Certain work environment's may be prone to slips, trips and falls.
Current systems use mechanical means to automatically lock.
Releasing the lock may be difficult after an STF.
Personnel may get suspension trauma.

4. Hardware Solenoid Seatbelt Tether Accelerometer Arduino ZigBee Modules
Encoder

5. Solenoid Requires NPN Transistor TIP120 Diode for current protection
12-24V up to 6A

6. Encoder Use of Arduino external interrupts
Implements function at each interrupt

7. Methodology Module One Module Two
Accelerometer: to measure slip, trips, falls
ZigBee: to communicate STF values
Encoder: to measure the tethers rotational velocity
Solenoid: to lock/unlock the tether
ZigBee: to communicate STF values

8. Flow Chart Lock Tether Set point STF Encoder Input Accelerometer Input
Velocity Conversions
Lock Tether
Flow Chart

9. Encoder

10. Velocity First order approximation with preset time interval
Encoder to return position based on four different possible states

11. Angular Velocity Angular_Velocity() will be executed on interval
Solenoid state determined from STF and RPM set point

12. Angular Velocity Determine if we are extending the tether
Determine If we are reading encoder pulses
Calculating RPM

13. Linear Velocity
Scale is linear correlation of voltage offset for each -/+ g felt by sensor
If free fall is detected send true value

14. Prototype Improvements
Addition of “super positon” sensors.
Determine pattern for STF
Use of multiple sensors
Implementation of boon sweeping

15. Crane Tether Mechanism
Cole Perrault
Spring 2016
ET 493
Ho-Hoon Lee
Cris Koutsougeras