Xem mẫu
- Evaluating DC Motors
Xác định momen thiết kế
Acquiring the Data
Data Requirements
No Load RPM
Stall Torque
Caution: Wear Eye Protection. Work with Adult
supervision.
- Graphing the Data
Mark max Torque Y Axis
Mark Max RPM X Axis
X Connect the points
with a straight line
X
- Graphing the Data
Locate the Mid Point RPM
Trace a horizontal line to the Y Axis
X
This is the Design Torque Value
X
X
Mid Point RPM
Determining Design Torque
ALWAYS Record, Describe and Date the Data
- Directly Measuring Motor Stall
Torque is a Learning
Experience.
Sample Motor 12V Battery Voltmeter
Ammeter
NC MO Switch
//-------------------------------
- Evaluating DC Motors
Determining Motor Stall Current
Measuring Armature Coil
Resistance
The Multi-Meter
selector is set to read
resistance in units
called ohms Ω (The Blue
portion of the selection dial)
The selector is set to
the lowest range (0-
200Ω )
The Value measure is
0.9 ohms.
- Measuring Armature Coil
Resistance
Set the meter to read ohms. Use
the lowest range.
Short the meter leads and
record the value. This is the
meter error value.
Attach your meter to the two
motor leads.
Slowly turn the armature shaft
and record values at 45°
intervals. Average these values.
Caution: Turning the armature shaft quickly, induces a
current in the armature windings. This Will damage the
meter.
Calculate the Stall Current
I= E Ohm’s Law
The basic Algebra of electronics
R
I = Current in Amperes
E = Voltage
R = Resistance in Ohms, Ω
- Calculate the Motor
Stall Current
The sample motor yields an average measured resistance value
of 0.6 Ω.
The intended BattleBot power supply will provide 12 Volts
emf (electro motive force).
The meter error = 0.3 Ω
E 12V
I= 40 amps =
R 0.6 Ω - 0.3 Ω
Predicted Motor Stall Current = 40 Amperes
Directly Measuring Motor Stall
current is a Learning
Experience.
Sample Motor 12V Battery Voltmeter
Ammeter
NC MO Switch
//-------------------------------
- Evaluating DC Motors
Determining Motor Stall Torque
and
No Load RPM
The Test Bench Set Up
Requirements
Securely fasten motor to
the Test Bench.
Use #10 AWG or larger,
Multi Stranded Wire.
Battery or Batteries similar
to those intended for use in
the BattleBot.
HD Automotive Starter
Switch
Caution: Testing motor torque creates strong
electrical and mechanical forces. Wear Eye
Protection. Work with Adult supervision.
- Special Equipment
Build a motor torque arm
Use 1”x1”x1/16” steel angle
3/8” Shaft Collar
Create the Stall Condition
Wear Eye Protection
3 People should
perform the test.
Set up and hold the
scale
Mark the scale
Energize/de-energize
the system.
- Set Up and Hold the Scale
Wear Eye Protection
Scale with Taped
Marking
Torque Arm
Retainer
Motor
Torque Arm
Create the Stall Condition
Wear Eye Protection
Procedure
Assume the stations;
Energizer
Scale holder
Scale marker
Energize the System
Raise the Torque Arm
with the Scale
Mark the Scale
Deflection
De-Energize.
ALWAYS Record, Describe and Date the Data
- Determining the Torque Value
F = Force (lbs.) 3 lbs
D = Length (ft.) .5 ft
Q = Torque (ft.lbs.)
F
D
Q= DxF
1.5 ft.lbs. = .5 ft. x 3 lbs.
ALWAYS Record, Describe and Date the Data
Measure No Load RPM
Wear Eye Protection
Procedure
Mark Armature Shaft
with Reflective Tape.
Energize the System
Read the No Load RPM
De-Energize.
ALWAYS Record, Describe and Date the Data
- Directly Measuring Motor Stall
Torque is a Learning
Experience.
Sample Motor 12V Battery Voltmeter
Ammeter
NC MO Switch
//---------------------------------------
- Evaluating DC Motors
Determining Robot Speed
- Robot Speed Equations
Use this equation to predict the BattleBot’s speed
ALWAYS Record, Describe and Date the Data
\\-------------------------------
- Evaluating DC Motors
Determining Gear Reduction
Determine the Required Tractive
Force
Procedure
Load a wheeled drive platform
with the design weight.
Approximate the correct weight
distribution.
Drag the platform by a spring
scale attached with a rope. Try
to drag level with the floor.
Tractive Force = 14 lbs.
ALWAYS Record, Describe and Date the Data
- Calculate the Required
Reduction
Tractive Force Required (lbs.)
Design Torque (ft.lbs.
= Approximate
Reduction
Drive Wheel Radius (ft.)
14 lbs
.75 ft. lbs
= 4.6 rounds off to 5:1
.25 ft.
ALWAYS Record, Describe and Date the Data
nguon tai.lieu . vn