Kinetostatic Motor Torque and Speed dialog-box - MD14.2

Note: This topic has been updated to describe the new functionality in MD14.2



Note: The options for a Linear Motor with a Slide-Joint will become available in a later release.


btn_delkeywordTo Open the Kinetostatic Torque and Speed dialog-box

Make sure:

You will see the Motor-Symbol at a jointRed-14-1b - see image below.

If you want the Motor and Gearbox to be at a different joint, then use:

Force toolbar > Configure Power Source to move the motor to the correct joint.

DoubleClick-GA-MotorElement

To see the Motor-Symbol, you must use: Force toolbar > Show Force

1.Click the Motor-SymbolRed-14-1b in the graphic-area

The Pin-Joint shows in the Selection-Window

2.Right-Click the Pin-Joint
3.Click Edit element in the contextual-menu

- or -

See How to open a dialog-box

The Kinematic Torque and Speed dialog-box opens.

btn_delkeywordApplication (Load) Torque vs Speed plot
FOUR QUADRANT: TORQUE(LOAD) vs SPEED

FOUR QUADRANT: TORQUE(LOAD) vs SPEED

When you open the Kinetostatic Torque-Speed dialog, you will see a plot of the Application (or Load) Torque vs Speed in all Four-Quadrants.


Four-Quadrant - Why 4 Quadrants

Many mechanism applications, when inertia is a significant or dominant load, require the servo-motor to apply:

Positive Torque - when accelerating in the positive direction and also decelerating in the reverse-direction
Negative Torque - when decelerating in the positive direction and also accelerating in the reverse-direction.
Positive angular velocity  - when advancing the mechanism
Negative angular velocity  - when returning the mechanism

btn_delkeywordSTEP 1: Auto-Filter and Range-Factor
1.Auto-Filter check-box

The Auto-Filter check-box is at the Top and Right of the dialog.

Auto-Filter OFF

When Auto-Filter is off, you can select from 1000s of Gearboxes.

Auto-Filter ON

Click the check-box to make the Auto-Filter active. We recommend you select Auto-Filter.

Auto-Filter ON, : MechDesigner offers for selection only those Gearboxes that have, as a Lower-Limit, the Torque and Speed capacity to drive the Application Load.

The Upper-Limit of Gearboxes that MechDesigner presents for selection is determined with the Range-Factor.


2.Range-Factor

The Range-Factor is bottom and left of the dialog.

Auto-Filter ON pre-filters Gearboxes to those that have as a minimum capacity the Torque and Speed capacity to drive the Application (Load)

Range-Factor pre-filters Gearboxes to those do not exceed Application-Load × Range-Factor.

Dialog-TorqueSpeed-Range_Limit00

Example: Auto-Filter ON, Range-Factor: 1.3

Lower Gearbox Torque Capacity = Equivalent Application (Load) Torque (21.495 N.m.)

Upper Gearbox Torque Capacity = Range Factor × Equivalent Application (Load) Torque (1.3 × 21.495 = 27.944 N.m.)


btn_delkeywordSTEP 2: Select a Gearbox Manufacturer

Select a Gearbox Manufacturer Red-14-1b

There are four Gearbox manufacturers from which you can choose: APEX, Neugart, Vogel, and Wittenstein

Dialog-KinetoStatic-GearBoxManuONLY

Note: If you need us to list a different Gearbox Manufacturer, then please email us.

btn_delkeywordSTEP 3: Select a Gearbox Model

Select a Gearbox Model Red-14-2

Dialog-KinetoStatic-GearBox-AF1-RF1.3

When you select a Gearbox Manufacturer, and Auto-Filter is ON, and you have entered a Range-Factor, the list of Gearboxes is limited to those whose capacity can satisfy these in-equalities:

Red-14-1b

Manufacturer

The Selected Manufacturer

Red-14-2

Model

The Selected the Model.

Each manufacturer has a different model format.

Red-14-3

Series

Series - from the selected Model

Red-14-4

i

#

Gearbox Ratio

from the Model

Red-14-5

T2N

Nm

Rated Torque referred to Output Shaft

- data sheet -

Red-14-6

T2max

Nm

Max. Torque referred to Output Shaft

- data sheet -

Red-14-7

n2N

RPM

Rated Speed referred to Output Shaft

- data sheet / i -

Red-14-8

m2MAX

RPM

Max Speed referred to Output Shaft

- data sheet / i -

T2max T2MAX RF × T2max

Maximum Application (Load) Torque Maximum Output Torque of the Gearbox Range-Factor × Maximum Application (Load) Torque


T2m T2N RF × T2m

Equivalent  Application (Load) Torque Rated Output Torque Capacity of the Gearbox Range-Factor × Equivalent  Application (Load) Torque


n2max× i n1MAX

Maximum Application (Load) Speed × Gearbox Ratio (i) Maximum Input Speed of the Gearbox


n2n × i n1N

Average Application (Load) Speed (or Equivalent, Mean) × Gearbox Ratio (i) Rated Input Speed of the Gearbox


 

btn_delkeywordGearbox Parameters Check List.

Dialog-KinetoStatic-GearBox-C

When you select a Gearbox model, its Gearbox Parameters Summary Sheet will show. This form is read only.

There should be 4 × OK-tiny-11-15 to indicate that the Gearbox has the capacity to drive the Application Load and satisfies those 4 × requirements.

Red-14-6 Peak Torque ≥ Maximum Application (Load)

Red-14-5 Rated Torque ≥ Equivalent Application (Load) Torque

Red-14-8 (Max Output Speed) ≥ Maximum Application (Load) Speed

Red-14-7 (Rated Output Speed) ≥ Equivalent Application (Load) Speed


Notes: Parameters in ( ) are referred to the output-shaft from the Gear-Ratio and the listed data-sheet information.


Other Parameters include:

Backlash
Stiffness
Efficiency
Shaft Diameter - the input shaft diameter, which is not in the list until you select a Servomotor.
Inertia - referred to the input, which is not in the list until you select a Servomotor.
btn_delkeywordGearbox Output Torque vs Speed plot

Dialog-TorSpeed-4Quadrant-GearBox

When you select a Gearbox, the Torque (N.m.) vs Speed (RPM) plot changes to indicate whether the Gearbox has the  Capacity to drive the Application Load or not.

The colour code is :

Green : Torque AND Speed of the Load ≤ Rated Gearbox Capacity
Amber : Torque OR Speed of the Load ≥ Rated Gearbox Capacity ≤ Maximum Gearbox Capacity
Red : Torque OR Speed of the Load ≥  Maximum Gearbox Capacity

Dialog-TorSpeed-4Quadrant-GearBox-Limits

Gearbox Torque and Speed Limits.

The Show Gearbox Limits check-list box is above the Gearbox selection box.

Show Gearbox Limits OFF

The axes are auto-scaled to the Maximum Application Torque and Speed, at the output of the Gearbox.

Show Gearbox Limits ON

The axes are auto-scaled to the Maximum Torque and Speed Capacity, referred to the output of the Gearbox.

This helps you compare the Torque and Speed Capacity of the Gearbox with the Application Load.

The Limits of Torque and Speed are shown as boxes.

Before you select a servomotor, the limit boxes and their colour codes indicate the:

Dark Blue : Maximum Torque and Speed capacity of the Gearbox
Light-Blue : Rated (or Nominal) Torque and Speed capacity of the Gearbox
Light-Brown : Equivalent Torque and Speed of the Application Load
btn_delkeywordSTEP 4: Select a Servomotor Manufacturer

Select a Servomotor Manufacturer Red-14-1b

There are four many Servomotor manufacturers from which you can choose one.

When you select a Servomotor Manufacturer, MechDesigner finds those that have the Torque and Speed Capacity required by the Application Load.

Dialog-TorSpeed-ServoMotor-Limits

Note: If you need us to list a different Servomotor Manufacturer, then please email us.

btn_delkeywordSTEP 5: Select a Servomotor Model

Select a Servomotor Model

Dialog-TorSpeed-ServoMotor-Selected-A

When you select a Servomotor Manufacturer, and Auto-Filter is ON, and you have entered a Range-Factor, the list of Servomotor is limited to those whose capacity can satisfy these in-equalities:

Red-14-1b

Manufacturer

The Selected Manufacturer

Red-14-2

Model

The Selected the Model.

Each manufacturer has a different model format.

Red-14-3

Series

Series - from the Selected Model

Red-14-4

d1

mm

Motor Shaft Diameter

- data sheet -

Red-14-5

Tn

Nm

Rated Torque

- data sheet -

Red-14-6

Tmax

Nm

Max. Torque

- data sheet -

Red-14-7

Nn

RPM

Rated Speed

- data sheet -

Red-14-8

Nmax

RPM

Max Speed

- data sheet -

d1max D   d1min

The Servomotor Shaft Diameter, D, must fit directly into the Gearbox, d1.

Note: Most Precision Planetary Gearboxes can accept a range of shaft diameters at their input. The Gearbox inertia is referred to the input shaft, and is different for each shaft diameter.


Tmax Tmotmax RF × Tmax

Maximum Application Load Torque referred to the Gearbox input-shaft

 Maximum Servomotor Torque Capacity

Range-Factor × Maximum Application Load Torque referred to the Gearbox input shaft


Tm TN RF × Tm

Equivalent Application (Load) Torque referred to the Gearbox input-shaft

Rated Servomotor Torque Capacity

Range-Factor × Equivalent  Application (Load) Torque referred to the Gearbox input shaft


Tmax Tmotmax RF × Tmax

Maximum Application (Load) Torque referred to the Gearbox input-shaft  

Rated Servomotor Torque Capacity

Range-Factor × Equivalent  Application (Load) Torque referred to the Gearbox input shaft


n1max Nmax

Maximum Application Speed referred to the Gearbox input-shaft Maximum Servomotor Speed


nN NN

Average Application (Load) Speed (or Equivalent, Mean) Rated Servomotor Speed

btn_delkeywordServomotor Parameters Check List.

Dialog-TorSpeed-ServoMotor-Parameters

When you select a Gearbox model, its Gearbox Parameters Summary Sheet will show. This form is read only.

There should be 4 × OK-tiny-11-15 to indicate that the Gearbox has the capacity to drive the Application Load and satisfies those 4 × requirements.

Peak Servomotor Torque ≥ Maximum Application (Load) ÷ i

Rated Servomotor Torque ≥ Equivalent Application (Load) Torque ÷ i

Max Servomotor Speed ≥ Maximum Application (Load) Speed × i

Continuous Servomotor Speed ≥ Equivalent Application (Load) Speed × i

Rated Power > Nominal Load Power.


Other Parameters include:

Vdc - Bus Voltage for Drive
Jm - Servomotor Inertia
D - Servomotor shaft diameters.
btn_delkeywordServomotor Torque vs Speed plot

Dialog-TorSpeed-ServoMotor-Graph Plot

When you select a Gearbox, colours of the dots for the Torque (N.m.) vs Speed (RPM) plot changes to indicate whether the Gearbox has the Capacity to drive the Application Load or not.

The colour code is :

Green : Torque AND Speed of the Load ≤ Rated Servomotor Capacity
Amber : Torque OR Speed of the Load ≥ Rated Servomotor Capacity ≤ Maximum Servomotor Capacity
Red : Torque OR Speed of the Load ≥  Maximum Servomotor Capacity

Dialog-TorSpeed-ServoMotor-Graph Plo-Limitst

Motor Torque and Speed Limits.

The Show Motor Limits check-list box is above the Motor selection box.

Show Motor Limits OFF

The axes are auto-scaled to the Maximum Torque and Speed, at the Servomotor Drive Shaft.

Show Motor Limits ON

The axes are auto-scaled to the Maximum Torque and Speed Capacity of the Selected Servomotor

This helps you compare the Torque and Speed Capacity of the Servomotor with the Application Load referred to its input-shaft.

The Limits of Torque and Speed are shown as boxes.

 Purple  : Maximum Torque and Speed capacity of the Servomotor
 Pink : Rated (or Nominal) Torque and Speed capacity of the Servomotor
Light-Brown : Equivalent Torque and Speed of the Application Load

tog_minusWhy the motor torque is different to the mechanism torque

The Torque we show in the graphic-area when we Display Force Vectors is the torque to move the mechanism only.

It does not include the Torque to move the motor and gearbox. It is necessary to add the Torque to accelerate the motor and the gearbox to Torque in the graphic-area.

Clearly, the Torque to move motor depends on the ....inertia of the motor and gearbox as well as the gearbox ratio.

The higher the gear ratio, the less Torque the motor 'sees'. But the motor must run faster and accelerate more. This influences the overall power, as well as system efficiency.

tog_minusMore on Torque vs Speed Curves

The performance characteristics of a brushless servo motor (motor/drive combination) are described by a torque/speed operating envelope.

As shown below, the coloured areas of the curve identify the Exceeded Duty, Continuous Duty and Intermittent Duty zones of the system.

Exceeded Duty

To move the mechanical system, the gearbox and itself, the servomotor must exceeds its maximum speed or the maximum torque, or both.

Continuous Duty Zone (S1)

The continuous duty zone is bordered by the maximum continuous stall torque up to the intersection with the intermittent duty line. The continuous torque line is set by either the motor’s maximum rated temperature, or the drive's rated continuous current output, whichever is less.

The system maximum continuous or 'voltage line' is set by the voltage rating of the drives, the line voltage supplied, and the motor winding.

The system can operate on a continuous basis anywhere within this area, assuming the ambient temperature is 40°C or less.

Intermittent Duty Zone (S5)

The intermittent duty zone is bordered by the peak stall torque and the system voltage line. The peak torque line is set by either the drives’ peak current rating, which the drive can give for a limited time, or the maximum rated peak current for the motor, whichever is less. Higher torque levels may be achievable at higher power levels.

Typical Torque / Speed Duty Capability of a Brushless Servomotor.

Typical Torque / Speed Duty Capability of a Brushless Servomotor.

Peak Torque: (ԎPS ) The Peak Torque the Motor and Gearbox at Stall Speed

Continuous Stall Torque: (ԎCS ). The Continuous Torque the Motor and Gearbox can give Continuously at Stall Speed.

Maximum Speed: (ωMAX ) Maximum possible speed of the Motor and Gearbox. Not attainable when the voltage is limited by the drive.

Knee Speed: (ωK ) The Speed at 'knee' in peak envelope that is the intersection of the Peak Torque with the Voltage Torque/Speed Limit Line.


Motor Providers also give a Rated Power - this is dependent on the Drive.

Continuous Rated Torque:(ԎCR ). The Continuous Torque at the Speed of the Rated Power.

Rated Speed: (ωR ) The Rated Speed or Speed at Rated Power. The motor can operate at this speed with the supply voltage.

tog_minusHow we calculate the Motor Torque and Motor Speed

The Reflected Inertia at the Motor shaft usually continuously changes in a machine-cycle.

With Constant Inertia Mechanical Systems it is easy to calculate Inertia Torque.

With mechanisms, the Torque is dependent on reflected inertia that is a function of Acceleration, Velocity, and Position.

PSMotion has developed algorithms to calculate these, which give a true indication of the reflected inertia at a motor shaft for even the most complex mechanisms.

The equations below, are calculated at every instant in a machine-cycle.

Typically, you aim to make the Reflected Load Inertia = (Motor + Gearbox) Inertia.

However, when the Load Inertia is not constant, it is more difficult to select the Motor and Gearbox.

Speed:

ωm = N × ωL

αm = N . αL


Torque

Tm = - αm (JG + JM) + sign(TVD)

TL = (TMD  ∕  N )  ∕  η

TT = Tm +  TL

N    = Gear Ratio

ωm = Motor Angular Velocity

ωL  = Load Angular Velocity

TT   = Total Torque

Tm  = Motor Torque

TL  = Load referred to Motor Shaft

TVD = Viscous 'Drag' Torque. It is always opposite to the direction of motion

TMD = Torque derived by MechDesigner at Motor Shaft ( f{PL , ωL, αL } )

JG   = Inertia of Gearbox

JM   = Inertia of Motor

αm  = Motor Acceleration

αL = Load Acceleration

η    = Gearbox Efficiency


Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd