US 11,795,661 B2
Method of controlling a rotatable load, a hydraulic system and a working machine
Mika Sahlman, Tampere (FI); and Kim Heybroek, Kvicksund (SE)
Assigned to VOLVO CONSTRUCTION EQUIPMENT AB, Eskilstuna (SE)
Appl. No. 17/612,875
Filed by Volvo Construction Equipment AB, Eskilstuna (SE); and Norrhydro Oy, Rovaniemi (FI)
PCT Filed May 21, 2019, PCT No. PCT/EP2019/063094
§ 371(c)(1), (2) Date Nov. 19, 2021,
PCT Pub. No. WO2020/233793, PCT Pub. Date Nov. 26, 2020.
Prior Publication US 2022/0220702 A1, Jul. 14, 2022
Int. Cl. E02F 9/22 (2006.01); E02F 9/12 (2006.01); F15B 13/02 (2006.01)
CPC E02F 9/2235 (2013.01) [E02F 9/123 (2013.01); E02F 9/2228 (2013.01); E02F 9/2296 (2013.01); F15B 13/02 (2013.01); E02F 9/2267 (2013.01); E02F 9/2292 (2013.01)] 24 Claims
OG exemplary drawing
 
1. A method of controlling a rotatable load by a hydraulic system, the hydraulic system comprising a high-pressure side; a low-pressure side; a variable displacement hydraulic machine for rotationally driving the rotatable load; and a valve arrangement in fluid communication with the high-pressure side, the low-pressure side, a first side of the hydraulic machine, and a second side of the hydraulic machine; wherein the method comprises:
determining when the hydraulic system is in a first operating state or a second operating state, the determination being based at least on one of a commanded or actual rotational speed of the hydraulic machine, a commanded or actual torque of the hydraulic machine, and/or a commanded or actual power of the hydraulic machine;
controlling the rotatable load in a valve control mode when the hydraulic system is in the first operating state, the valve control mode comprising controlling the rotatable load by controlling the valve arrangement;
controlling the rotatable load in a displacement control mode when the hydraulic system is in the second operating state, the displacement control mode comprising controlling the rotatable load mainly by controlling the displacement of the hydraulic machine; and
applying a non-zero absolute minimum displacement limitation to the hydraulic machine at least in the valve control mode.
 
15. A hydraulic system for controlling a rotatable load, the hydraulic system comprising:
a high-pressure side;
a low-pressure side;
a variable displacement hydraulic machine for rotationally driving the rotatable load; and
a valve arrangement in fluid communication with the high-pressure side, the low-pressure side, a first side of the hydraulic machine and a second side of the hydraulic machine;
wherein the hydraulic system further comprises a control system configured to:
determine when the hydraulic system is in a first operating state or a second operating state, the determination being based at least on one of a commanded or actual rotational speed of the hydraulic machine, a commanded or actual torque of the hydraulic machine, and/or a commanded or actual power of the hydraulic machine;
control the rotatable load in a valve control mode when the hydraulic system is in the first operating state, the valve control mode comprising controlling the rotatable load by controlling the valve arrangement;
control the rotatable load in a displacement control mode when the hydraulic system is in the second operating state, the displacement control mode comprising controlling the rotatable load mainly by controlling the displacement of the hydraulic machine; and
applying a non-zero absolute minimum displacement limitation to the hydraulic machine at least in the first operating state.