3. Select the motors from the Internet, and provide the specifications. Show the logic in selecting them. Identify all the parameters needed. Guess/estimate those that you could not find.
The logic behind selecting the right servo motor is given below:-
Motion type—whether an actuator has a circular or a linear motion path, rotates continuously or within a limited range. You need a continuous rotation servo motor for a robot to get around on wheels. When your task is to make a machine do pull or push movements, your choice is the linear type.
Precision—how accurate a mechanism translates input signals into output shaft positions. Accuracy depends much on the feedback device. Servos can incorporate a potentiometer, an encoder, a resolver, or a Hall sensor. Absolute and incremental encoders are believed to provide the highest precision.
Speed—how fast a motion solution accomplishes a single positioning task. Pay attention to the design of the motion core. Key factors are the motor dimensions, winding size and resistance, as well as the size and type of magnets.
Strength—how much rotational or linear force it generates. A handy tool in selecting an appropriate robot actuator is a speed-torque curve illustrating how amounts of produced force change over time. The continuous duty zone in the curve represents those speed-torque combinations where performance is optimal.
Break strength—what is the limit load that a servo can handle. Refer to the permissible load inertia value. At loads exceeding the limit, various issues are probable, such as unstable control, vibration, etc.
Size and weight—how well an actuator fits into a robot configuration. The dimensional range of currently available solutions includes: nano, micro, pico, as well as standard, large, and so-called “giant scale” models.
Bearing type—servos have have either bushings or one or more ball bearings on the output shaft. Bearings affect precision and smoothness of operation. Ball-bearing mechanisms are less wear-prone and can maintain the same accuracy level throughout their service life.
Gearbox specifications—the gear ratio, the backlash, and material of the gearing mechanism. The gear ratio is the proportional difference between the speed and rotational force at the gearhead input and that at its output. Backlash is amount of free play between mating gear teeth. Since the value influences positioning accuracy, it should be as close to zero as possible.
Gears are typically made from plastic, karbonite, or metal. Plastic ones are lightweight, but unsuitable for heavy-duty applications. Karbonite is the most long-lasting option, but expensive. Metal gears are the heaviest, but they can handle considerable loads.
As torque is calculated above = 63.75kgcm2/sec2
I.e. T=0.006375 Nm
Based on the above torque value selecting servomotor which can be used in all the three joints
Specifications:-
Model - RDrive 50
Power-65 W
Rated Torque-11 Nm
Peak torque-28 Nm
Rated rotation speed-55 rpm
Diameter- 53 mm
Length- 88, 1 mm
Hollow shaft diameter – 9mm
Weight – 550g
Voltage - 48 V
Work conditions - 0 °C to +35 °ะก
Interface - CANopen
API - C/C++/Java/Python
Encoder - 2x19 bit, magnetic, absolute position
4. now develop the overall control system to carry out the task, and show the results of the controller.
Overall Control System:-
6. Appendices
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Appendix A |
Sorting Given Data |
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Appendix B |
Logic |
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Appendix C |
Finding Angle Joints of Diagonal |
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Appendix D |
Velocity, Acceleration, Torque |
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Appendix E |
Robot Design |
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Appendix F |
Motor Selection |
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Appendix G |
Overall Control System |
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