Electric-driven Zonal Hydraulics in Non-Road Mobile Machinery
2. Description of test setup
The experimental setup uses a speed-controlled electric servo motor drive rotating two hydraulic pumps to directly control the amount of hydraulic oil pumped to the asymmetrical double-acting cylinder MIRO C-10-60/30× 400. The simplified circuit diagram of the experi‐
mental test setup is illustrated in Figure 4. The hydraulic pump/motors P1 and P2 create an input and output flow that depends on the rotating speed of the servo motor. The oil pressure rises to the required level as determined by the payload. During lowering motion, the potential energy of the payload creates a flow that rotates the hydraulic machine P1 as a motor and the hydraulic machine P2 as a pump, and the mechanically connected electric motor acts as a generator, which is controlled by the frequency converter. The speed-controlled generator controls the amount of fluid flow and the position of the payload. The program for the electric drive controls both the electrical and hydraulic sides of the system as there is no conventional valve control.
For easier understanding of the real displacements of the pumps, the following ratios RA and RQ will be defined. In this work, the ratio between the cylinder areas is defined by the following equation:
3 1 A , R A
=A
where A3=A1−A2 is the cylinder area from the rod side. The diameter of the cylinder piston head is d1 = 0.06 m and d2 = 0.03 m is the diameter of the piston rod, which determines the piston surface areas A1 and A2. According to the datasheet, the cylinder stroke is l = 0.4 m.
As previously stated, the pump/motors P1 and P2 are mounted on the same axis, so their speeds are identical. If the pump leakage is ignored, the ratio of the flow rates RQ can be produced directly from the displacement of the pump/motors D1 and D2.
Q 2 1
D . R =D
Figure 4 illustrates the first prototype of the DDH setup with RQ≈0.63 and RA=0.75. To test the concept, the components for this prototype were taken off the shelf.
4
As previously stated, the pump/motors P1 and P2 are mounted on the same axis, so their speeds are identical. If the pump leakage is ignored, the ratio of the flow rates RQ can be produced directly from the displacement of the pump/motors D1 and D2.
ܴ୕ൌܦଶ
ܦଵǤ (2)
Figure 4 illustrates the first prototype of the DDH setup withܴ୕ൎ ͲǤ͵ and ܴൌ ͲǤͷ. To test the concept, the components for this prototype were taken from the shelf.
(a) (b) (c)
M a
b c
d
e H
f
g h i
j k
l
m P2
P1
Figure 4. First prototype of the DDH setup: (a) zoom view; (b) the experimental setup consists of (a) a double-acting cylinder, (b) wire-actuated encoder, (c) pressure sensor, (d) reversible gear pump/motor P1, (e) pressure sensor, (f) gearbox, (g) PMSM motor/generator, (h) current sensors, (i) frequency converter, (j) tank, (k) pressure sensor, (l) reversible gear pump/motor P2 and (m) pressure sensor in the tank line;
(c) the crane is used for the DDH setup as a test platform (side view).
Two XV-2M internal gear pump/motors by Vivoil with displacements of 14.4 and 22.8 cm3/rev were used, P2 and P1, respectively [20]. The position feedback from the motor is given by means of its in-built incremental encoder (4096 pulses per revolution, resolution 14 bits), and read with the Unidrive SP1406 drive software [21]. It converts the AC power supply from the line and allows the speed of the permanent magnet brushless servo motor, Unimotor 115U2C manufactured by Emerson Control Techniques, to be set, taking advantage of the information obtained by the feedback device fitted to ensure the rotor speed is exactly as demanded [22]. This experimental setup was tested with a payload of 150 kg at motor speed ranges from 300 to 500 rpm. Figure 5 shows an example of measured data for a motor speed of 400 rpm and a payload of 150 kg: speed, torque and pressure.
Figure 4. First prototype of the DDH setup: (a) zoom view;(b) the experimental setup consists ofa) a double-acting cyl‐
inder, b) wire-actuated encoder, c) pressure sensor, d) reversible gear pump/motor P1, e) pressure sensor, f) gearbox, g) PMSM motor/generator, h) current sensors, i)frequency converter, j) tank, k) pressure sensor, l) reversible gear pump/
motor P2 and m) pressure sensor in the tank line; (c) the crane is used for the DDH setup as a test platform (side view).
Two XV-2M internal gear pump/motors by Vivoil with displacements of 14.4 and 22.8 cm3/rev were used, P2 and P1, respectively [20]. The position feedback from the motor is given by means of its in-built incremental encoder (4096 pulses per revolution, resolution 14 bits), and read
For easier understanding of the real displacements of the pumps, the following ratios RA and RQ will be defined. In this work, the ratio between the cylinder areas is defined by the following equation:
3 1 A , R A
= A
where A3=A1−A2 is the cylinder area from the rod side. The diameter of the cylinder piston head is d1 = 0.06 m and d2 = 0.03 m is the diameter of the piston rod, which determines the piston surface areas A1 and A2. According to the datasheet, the cylinder stroke is l = 0.4 m.
As previously stated, the pump/motors P1 and P2 are mounted on the same axis, so their speeds are identical. If the pump leakage is ignored, the ratio of the flow rates RQ can be produced directly from the displacement of the pump/motors D1 and D2.
Q 2 1
D . R = D
Figure 4 illustrates the first prototype of the DDH setup with RQ≈0.63 and RA=0.75. To test the concept, the components for this prototype were taken off the shelf.
4
As previously stated, the pump/motors P1 and P2 are mounted on the same axis, so their speeds are identical. If the pump leakage is ignored, the ratio of the flow rates RQ can be produced directly from the displacement of the pump/motors D1 and D2.
ܴ୕ൌܦଶ
ܦଵǤ (2)
Figure 4 illustrates the first prototype of the DDH setup withܴ୕ൎ ͲǤ͵ and ܴൌ ͲǤͷ. To test the concept, the components for this prototype were taken from the shelf.
(a) (b) (c)
M a
b c
d
e H
f
g h i
j k
l
m P2
P1
Figure 4. First prototype of the DDH setup: (a) zoom view; (b) the experimental setup consists of (a) a double-acting cylinder, (b) wire-actuated encoder, (c) pressure sensor, (d) reversible gear pump/motor P1, (e) pressure sensor, (f) gearbox, (g) PMSM motor/generator, (h) current sensors, (i) frequency converter, (j) tank, (k) pressure sensor, (l) reversible gear pump/motor P2 and (m) pressure sensor in the tank line;
(c) the crane is used for the DDH setup as a test platform (side view).
Two XV-2M internal gear pump/motors by Vivoil with displacements of 14.4 and 22.8 cm3/rev were used, P2 and P1, respectively [20]. The position feedback from the motor is given by means of its in-built incremental encoder (4096 pulses per revolution, resolution 14 bits), and read with the Unidrive SP1406 drive software [21]. It converts the AC power supply from the line and allows the speed of the permanent magnet brushless servo motor, Unimotor 115U2C manufactured by Emerson Control Techniques, to be set, taking advantage of the information obtained by the feedback device fitted to ensure the rotor speed is exactly as demanded [22]. This experimental setup was tested with a payload of 150 kg at motor speed ranges from 300 to 500 rpm. Figure 5 shows an example of measured data for a motor speed of 400 rpm and a payload of 150 kg: speed, torque and pressure.
Figure 4. First prototype of the DDH setup: (a) zoom view;(b) the experimental setup consists ofa) a double-acting cyl‐
inder, b) wire-actuated encoder, c) pressure sensor, d) reversible gear pump/motor P1, e) pressure sensor, f) gearbox, g) PMSM motor/generator, h) current sensors, i)frequency converter, j) tank, k) pressure sensor, l) reversible gear pump/
motor P2 and m) pressure sensor in the tank line; (c) the crane is used for the DDH setup as a test platform (side view).
Two XV-2M internal gear pump/motors by Vivoil with displacements of 14.4 and 22.8 cm3/rev were used, P2 and P1, respectively [20]. The position feedback from the motor is given by means of its in-built incremental encoder (4096 pulses per revolution, resolution 14 bits), and read
with the Unidrive SP1406 drive software [21]. It converts the AC power supply from the line and allows the speed of the permanent magnet brushless servo motor, Unimotor 115U2C manufactured by Emerson Control Techniques, to be set, taking advantage of the information obtained by the feedback device fitted to ensure the rotor speed is exactly as demanded [22].
This experimental setup was tested with a payload of 150 kg at motor speed ranges from 300 to 500 rpm. Figure 5 shows an example of measured data for a motor speed of 400 rpm and a payload of 150 kg: speed, torque and pressure.
Figure 5. Example of measured data of the first DDH prototype: motor speed, torque, pressure in the pump/motor line P1 and in the pump/motor line P2. For a motor speed of 400 rpm and a payload of 150 kg.
In Figure 5, during the lifting, which lasts from 1 to 7 s, the pressure in the pump/motor P1 is about 2 MPa, which rises by the end to 4 MPa. It is worth remarking that the rise appears to be due to the difference between RQ and RA. A similar rise also occurs in the pump/motor line P2, from atmospheric pressure to 2.6 MPa.
During the lowering, performed from 7 to 13 s, a drop in the pressure from high pressure to about 1 MPa happens. During the lifting, the motor torque is 7 Nm; during the lowering, the torque is around 1 Nm. The pressure in the tank line is close to atmospheric pressure, as it is supposed to be in an open system.
In order to overcome the rise in pressure at the end of the movement and investigate the tankless approach, a new prototype was designed. Figure 6 illustrates the experimental test setup of the second DDH prototype. The system is closed by giving up the tank completely (compare to Figure 2b) and replacing it with a hydraulic accumulator A.
6
(a) (b)
M a
b c d
e H
f g
h i
j k
l
m n
A B
P2 P1
Figure 6. (a) Schematics of the setup of the second DDH prototype: (a) double-acting cylinder, (b) wire-actuated encoder, (c) pressure sensor, (d) flow meter, (e) reversible gear pump/motor P1, (f) PMSM motor/generator, (g) reversible gear pump/motor P2, (h) pressure sensor, (i) hydraulic accumulator B, (j) pressure sensor in tank line, (k) current sensors, (l) frequency converter, (m) pressure sensor and (n) hydraulic accumulator A; (b) photograph of DDH setup.
Within the framework of this work for the second prototypeܴ୕ൎ ͲǤ͵ andܴൌ ͲǤͷ . It can be seen that the ideal RQ = RA was not achieved. Therefore, an accumulator B is added to compensate for the displacement difference between the available pump/motors and cylinder areas.
Components used
In the second prototype, DDH setup an electric motor, an IndraDyn T MST130A-0250-N torque motor from Bosch Rexroth, is used. The parameters of the electric motor are shown in Table 1.
Table 1. IndraDyn T MST130A-0250-N parameters [23].
Rated power Rated
torque Maximum
torque Nominal
speed Maximum
speed Pole
pairs Torque
constant Voltage
constant Resistance Inductance 1.2kW 4.5
Nm 13 Nm 2500
rpm 4000 rpm 10 1.3
Nm/A 0.085
V/min-1 5.9 Ohm 17.5 mH Bosch Rexroth AZMF-12-011U and AZMF-12-008U external gear motors are used as hydraulic pumps/motors.
The parameters of the pump/motors are shown in Tables 2 and 3.
Table 2. Parameters of the AZMF-12-011U hydraulic pump/motor P1 [24].
Flow rate Maximum
pressure Leakage-oil
pressure Minimum speed Maximum speed
ͳͳuͳͲି m3/rev 25 MPa 0.3 MPa* 500 Nm 3500 rpm
Table 3. Parameters of the AZMF-12-008U hydraulic pump/motor P2 [24].
Flow rate Maximum
pressure Leakage-oil
pressure Minimum speed Maximum speed
ͺuͳͲି m3/rev 25 MPa 0.3 MPa* 500 Nm 4000 rpm
* Short-term pressure during start 1 MPa.
Two Parker AD100B20T9A1 diaphragm accumulators are utilized as the initial choices. Table 4 shows the parameters of the hydraulic accumulators.
Figure 6. (a) Schematics of the setup of the second DDH prototype: a) double-acting cylinder, b) wire-actuated encod‐
er, c) pressure sensor, d) flow meter,e) reversible gear pump/motor P1, f) PMSM motor/generator, g) reversible gear pump/motor P2, h) pressure sensor, i) hydraulic accumulator B, j) pressure sensor in tank line, k) current sensors, l) frequency converter, m) pressure sensor and n) hydraulic accumulator A; (b) photograph of DDH setup.
Within the framework of this work for the second prototype RQ≈0.73 and RA=0.75. It can be seen that the ideal RQ = RA was not achieved. Therefore, an accumulator B is added to com‐
pensate for the displacement difference between the available pump/motors and cylinder areas.
2.1. Components used
In the second prototype, DDH setup an electric motor, an IndraDyn T MST130A-0250-N torque motor from Bosch Rexroth, is used. The parameters of the electric motor are shown in Table 1.
Rated power
Rated torque
Maximum torque
Nominal speed
Maximum speed
Pole pairs
Torque constant
Voltage
constant Resistance Inductance 1.2 kW 4.5 Nm 13 Nm 2500 rpm 4000 rpm 10 1.3 Nm/A 0.085 V/
min-1 5.9 Ohm 17.5 mH Table 1. IndraDyn T MST130A-0250-N parameters [23].
In order to overcome the rise in pressure at the end of the movement and investigate the tankless approach, a new prototype was designed. Figure 6 illustrates the experimental test setup of the second DDH prototype. The system is closed by giving up the tank completely (compare to Figure 2b) and replacing it with a hydraulic accumulator A.
6
(a) (b)
M a
b c d
e H
f g
h i
j k
l
m n
A B
P2 P1
Figure 6. (a) Schematics of the setup of the second DDH prototype: (a) double-acting cylinder, (b) wire-actuated encoder, (c) pressure sensor, (d) flow meter, (e) reversible gear pump/motor P1, (f) PMSM motor/generator, (g) reversible gear pump/motor P2, (h) pressure sensor, (i) hydraulic accumulator B, (j) pressure sensor in tank line, (k) current sensors, (l) frequency converter, (m) pressure sensor and (n) hydraulic accumulator A; (b) photograph of DDH setup.
Within the framework of this work for the second prototypeܴ୕ൎ ͲǤ͵ andܴൌ ͲǤͷ . It can be seen that the ideal RQ = RA was not achieved. Therefore, an accumulator B is added to compensate for the displacement difference between the available pump/motors and cylinder areas.
Components used
In the second prototype, DDH setup an electric motor, an IndraDyn T MST130A-0250-N torque motor from Bosch Rexroth, is used. The parameters of the electric motor are shown in Table 1.
Table 1. IndraDyn T MST130A-0250-N parameters [23].
Rated power Rated
torque Maximum
torque Nominal
speed Maximum
speed Pole
pairs Torque
constant Voltage
constant Resistance Inductance 1.2kW 4.5
Nm 13 Nm 2500
rpm 4000 rpm 10 1.3
Nm/A 0.085
V/min-1 5.9 Ohm 17.5 mH Bosch Rexroth AZMF-12-011U and AZMF-12-008U external gear motors are used as hydraulic pumps/motors.
The parameters of the pump/motors are shown in Tables 2 and 3.
Table 2. Parameters of the AZMF-12-011U hydraulic pump/motor P1 [24].
Flow rate Maximum
pressure Leakage-oil
pressure Minimum speed Maximum speed
ͳͳuͳͲି m3/rev 25 MPa 0.3 MPa* 500 Nm 3500 rpm
Table 3. Parameters of the AZMF-12-008U hydraulic pump/motor P2 [24].
Flow rate Maximum
pressure Leakage-oil
pressure Minimum speed Maximum speed
ͺuͳͲି m3/rev 25 MPa 0.3 MPa* 500 Nm 4000 rpm
* Short-term pressure during start 1 MPa.
Two Parker AD100B20T9A1 diaphragm accumulators are utilized as the initial choices. Table 4 shows the parameters of the hydraulic accumulators.
Figure 6. (a) Schematics of the setup of the second DDH prototype: a) double-acting cylinder, b) wire-actuated encod‐
er, c) pressure sensor, d) flow meter,e) reversible gear pump/motor P1, f) PMSM motor/generator, g) reversible gear pump/motor P2, h) pressure sensor, i) hydraulic accumulator B, j) pressure sensor in tank line, k) current sensors, l) frequency converter, m) pressure sensor and n) hydraulic accumulator A; (b) photograph of DDH setup.
Within the framework of this work for the second prototype RQ≈0.73 and RA=0.75. It can be seen that the ideal RQ = RA was not achieved. Therefore, an accumulator B is added to com‐
pensate for the displacement difference between the available pump/motors and cylinder areas.
2.1. Components used
In the second prototype, DDH setup an electric motor, an IndraDyn T MST130A-0250-N torque motor from Bosch Rexroth, is used. The parameters of the electric motor are shown in Table 1.
Rated power
Rated torque
Maximum torque
Nominal speed
Maximum speed
Pole pairs
Torque constant
Voltage
constant Resistance Inductance 1.2 kW 4.5 Nm 13 Nm 2500 rpm 4000 rpm 10 1.3 Nm/A 0.085 V/
min-1 5.9 Ohm 17.5 mH Table 1. IndraDyn T MST130A-0250-N parameters [23].
Bosch Rexroth AZMF-12-011U and AZMF-12-008U external gear motors are used as hydraulic pumps/motors. The parameters of the pump/motors are shown in Tables 2 and 3.
Flow rate Maximum pressure Leakage-oil pressure Minimum speed Maximum speed
11 ×10−6 m3/rev 25 MPa 0.3 MPa* 500 Nm 3500 rpm
Table 2. Parameters of the AZMF-12-011U hydraulic pump/motor P1 [24].
Flow rate Maximum pressure Leakage-oil pressure Minimum speed Maximum speed
8 ×10−6 m3/rev 25 MPa 0.3 MPa* 500 Nm 4000 rpm
* Short-term pressure during start 1 MPa.
Table 3. Parameters of the AZMF-12-008U hydraulic pump/motor P2 [24].
Two Parker AD100B20T9A1 diaphragm accumulators are utilized as the initial choices. Table 4 shows the parameters of the hydraulic accumulators.
Capacity (volume) Maximum pressure
0.001 m3 200 MPa
Table 4. Parameters of the AD100B20T9A1 hydraulic accumulators A and B.
The pressure was measured with Gems 3100R0400S pressure transducers. The velocity of the cylinder piston was measured with an SGW/SGI wire-actuated encoder by SIKO.
According to the manufacturer, the pump/motors used have an external leakage-oil line with a pressure limitation of 0.3 MPa. During the start, the maximum allowed short-term pressure is 1 MPa. Thus, a detailed investigation of the hydraulic connection of the external leakage line is required.