Current capability limiting of DC machines

Patent metadata

Field	Value
Publication number	US-10530282-B2
Application number	US-201715603671-A
Country	US
Kind code	B2
Filing date	May 24, 2017
Priority date	May 25, 2016
Publication date	Jan 7, 2020
Grant date	Jan 7, 2020

Abstract

An embodiment of a control system includes a current command module configured to receive a torque command and output a current command for controlling a direct current (DC) motor, and a current capability limiting module configured to receive the current command and a current limit indicating a maximum motor current, limit the current command based on the current limit, and actively further limit the current command based on a capability limit value.

First claim

Having thus described the invention, it is claimed:

1. A control system, comprising:
a current command module configured to receive a torque command and output a current command; and
a current capability limiting module configured to receive the current command and a current limit indicating a maximum motor current, limit the current command based on the current limit, and actively further limit the current command based on a capability limit value, and output a limited current command to control a brushed direct current (DC) motor;
wherein the capability limit value is determined based on a non-linear function and is distinct from the maximum motor current.

2. The system of claim 1 , further comprising a current regulator configured to apply a voltage to the brushed DC motor based on the limited current command.

3. The system of claim 1 , wherein the capability limit value includes a motor capability limit curve the specifies the capability limit value as a function of motor speed.

4. The system of claim 3 , wherein the capability limit value includes a maximum motor capability limit curve and a minimum motor capability limit curve.

5. The system of claim 1 , wherein the capability limit value is calculated based on a DC bus voltage.

6. The system of claim 5 , wherein the capability limit value includes a maximum motor current value (i cp ) based on a positive value of the DC bus voltage and a minimum motor current value (i cn ) based on a negative value of the DC bus voltage.

7. A control system, comprising:
a current command module configured to receive a torque command and output a current command; and
a current capability limiting module configured to receive the current command and a current limit indicating a maximum motor current, limit the current command based on the current limit, actively further limit the current command based on a capability limit value, and output a limited current command to control a direct current (DC) motor,
wherein the capability limit value is calculated based on a DC bus voltage, the capability limit value includes a non-linear maximum motor current value (i cp ) based on a positive value of the DC bus voltage and a non-linear minimum motor current value (i cn ) based on a negative value of the DC bus voltage, wherein the capability limit value is distinct from the maximum motor current, and
the maximum motor current value (i cp ) is calculated by solving a function ƒ(i cp ) represented by:

f
⁡

(

i
cp

)

=

i
cp

⁢
R

+

K
e

⁢

ω
m

+

σ
⁡

(

i
cp

)

⁢

V
0

⁡

(

1
-

e



i
cp



I
0

)

-

V
DC

=
0

wherein R is a resistance of the DC motor, K e is a motor voltage or torque constant, ω m is a rotational speed of the DC motor, V 0 is a voltage variable, I 0 is a motor current, V DC is the DC bus voltage, and

σ
⁡

(

i
cp

)

⁢

V
0

⁡

(

1
-

e



i
cp



I
0

)

is a brush drop voltage.

8. A control system, comprising:
a current command module configured to receive a torque command and output a current command; and
a current capability limiting module configured to receive the current command and a current limit indicating a maximum motor current, limit the current command based on the current limit, actively further limit the current command based on a capability limit value, and output a limited current command to control a direct current (DC) motor,
wherein the capability limit value is calculated based on a DC bus voltage, the capability limit value includes a nonlinear maximum motor current value (i cp ) based on a positive value of the DC bus voltage and a non-linear minimum motor current value (i cn ) based on a negative value of the DC bus voltage, wherein the capability limit value is distinct from the maximum motor current, and
the minimum motor current value (i cn ) is calculated by solving a function ƒ(i cn ) represented by:

f
⁡

(

i
cn

)

=

i
cn

⁢
R

+

K

Assignees

• Steering Solutions Ip Holding

Inventors

• Pramod Prerit
• Namburi Krishna Mohan Pavan
• Kleinau Julie Ann

Classifications

• H02P29/027

  the fault being an over-current · CPC title

• G05B2219/42296

  Detect diminishing torque of drive motor, below low limit · CPC title

• G05B2219/43204

  Different, dynamic current limits as function of speed · CPC title

• B60Y2400/602

  DC Machines · CPC title

• G05B19/416

  characterised by control of velocity, acceleration or deceleration (G05B19/19 takes precedence) · CPC title