Electrical motor control for high performance hydraulic systems
A control unit ( 150 ) for controlling a hydraulic system on a construction machine ( 100 ), where the hydraulic system comprises a hydraulic pump arrangement with an electric drive motor configured to drive a hydraulic pump at a controllable drive torque, wherein the control unit ( 150 ) is arranged to obtain a load pressure of at least one actuator in the hydraulic system, to convert the obtained load pressure into a corresponding torque, and to control the electric drive motor to generate the torque.
1 . A control unit for controlling a hydraulic system on a construction machine, wherein the hydraulic system comprises a hydraulic pump arrangement with an electric drive motor configured to drive a hydraulic pump at a controllable drive torque and/or controllable drive speed,
wherein the control unit is arranged to obtain a load pressure of at least one actuator in the hydraulic system, to map the obtained load pressure to a target drive torque or a target drive speed based on a mapping between the load pressure and the target drive torque or the target drive speed, and to control the electric drive motor to generate the target drive torque or the target drive speed, and
wherein the control unit is arranged to detect a type and/or identification of the hydraulic pump and to configure the mapping between the load pressure and the target drive torque or the target drive speed based on the pump type and/or identification.
2 . The control unit according to claim 1 , wherein the load pressure corresponds to a maximum load pressure in the hydraulic system, and wherein the target drive torque or the target drive speed is configured to generate an output pressure from the hydraulic pump in excess of the load pressure by a pre-determined margin pressure.
3 . The control unit according to claim 1 , wherein the load pressure is obtained from a pressure sensor arranged in connection to an actuator of the at least one actuator constituting a load of the hydraulic system.
4 . The control unit according to claim 1 , wherein the load pressure is mapped to the target drive torque or the target drive speed based on a look-up table, LUT, arranged accessible from the control unit.
5 . The control unit according to claim 1 , wherein the load pressure is mapped to the target drive torque or the target drive speed based on an analytical relationship between the load pressure and the target drive torque.
6 . The control unit according to claim 5 , wherein the analytical relationship between the load pressure and the target drive torque is given by
T
=
V
g
P
20
π
η
[
Nm
]
where V g is a displacement per revolution of the pump in cm 3 and η is a unitless hydraulic-mechanical efficiency parameter associated with the hydraulic pump arrangement.
7 . The control unit according to claim 5 , wherein the analytical relationship between the load pressure and the target drive torque is given by
T
=
V
g
P
20
π
η
+
d
ω
dt
J
[
Nm
]
where V g is a displacement per revolution of the pump in cm 3 , η is a unitless hydraulic-mechanical efficiency parameter associated with the hydraulic pump arrangement, J is a sum of moments of inertia of the pump and the electric drive motor, and ω is a rotational velocity of an electric drive motor axle.
8 . The control unit according to claim 1 , wherein the target drive torque of the drive motor is compensated for a delta-pressure of a load sensing hydraulics system.
9 . The control unit according to claim 1 , arranged to receive a signal from a pressure sensor arranged to measure an actual pump output pressure, and to verify that the actual pump output pressure is within an acceptable range from an expected pump output pressure resulting from the target drive torque or the target drive speed.
10 . The control unit according to claim 9 , wherein the control unit is arranged to adjust the mapping between the load pressure and the target drive torque, or the target drive speed based on the actual pump output pressure.
11 . The control unit according to claim 1 , wherein the control unit is configurable in a first mode of operation and in a second mode of operation, wherein the mapping associated with the first mode of operation is different than the mapping associated with the second mode of operation.
12 . A hydraulic system comprising the control unit according to claim 1 .
13 . The hydraulic system according to claim 12 , wherein the electric drive motor is a variable speed electric motor and the hydraulic pump is a fixed displacement hydraulic pump.
14 . A construction machine comprising the hydraulics system according to claim 12 .
15 . A control unit for controlling a hydraulic system on a construction machine, wherein the hydraulic system comprises a hydraulic pump arrangement with an electric drive motor configured to drive a hydraulic pump at a controllable drive torque and/or controllable drive speed,
wherein the control unit is arranged to obtain a load pressure of at least one actuator in the hydraulic system, to convert the obtained load pressure into a target drive torque or a target drive speed, and to control the electric drive motor to generate the target drive torque or the target drive speed,
wherein the control unit is arranged to receive a signal from a pressure sensor arranged to measure an actual pump output pressure, and to verify that the actual pump output pressure is within an acceptable range from an expected pump output pressure resulting from the target drive torque or the target drive speed.
16 . The control unit according to claim 15 , wherein the load pressure corresponds to a maximum load pressure in the hydraulic system, and wherein the target drive torque or the target drive speed is configured to generate an output pressure from the hydraulic pump in excess of the load pressure by a pre-determined margin pressure.
17 . The control unit according to claim 15 , wherein the load pressure is obtained from a pressure sensor arranged in connection to an actuator of the at least one actuator constituting a load of the hydraulic system.
18 . The control unit according to claim 15 , wherein the load pressure is mapped to the target drive torque or the target drive speed based on an analytical relationship between the load pressure and the target drive torque.
19 . A control unit for controlling a hydraulic system on a construction machine, wherein the hydraulic system comprises a hydraulic pump arrangement with an electric drive motor configured to drive a hydraulic pump at a controllable drive torque and/or controllable drive speed,
wherein the control unit is arranged to obtain a load pressure of at least one actuator in the hydraulic system, to convert the obtained load pressure into a target drive torque or a target drive speed, and to control the electric drive motor to generate the target drive torque or the target drive speed,
wherein the load pressure is converted into the target drive torque or the target drive speed based on an analytical relationship between the load pressure and the target drive torque,
wherein the analytical relationship between the load pressure and the target drive torque is given by
T
=
V
g
P
20
π
η
[
Nm
]
where V g is a displacement per revolution of the pump in cm 3 and η is a unitless hydraulic-mechanical efficiency parameter associated with the hydraulic pump arrangement, or
wherein the analytical relationship between the load pressure and the target drive torque is given by
T
=
V
g
P
20
π
η
+
d
ω
dt
J
[
Nm
]
where V g is a displacement per revolution of the pump in cm 3 , η is a unitless hydraulic-mechanical efficiency parameter associated with the hydraulic pump arrangement, J is a sum of moments of inertia of the pump and the electric drive motor, and ω is a rotational velocity of an electric drive motor axle.