Example: dynamics of an asphalt spreader hydraulic drive

As an example we’ll consider presented on Fig. 11 а the simplified circuit of a hydraulic drive of an asphalt spreader. The circuit consists of three hydraulic contours working simultaneously: a hydraulic drive of rise-lowering of the pressing plate, executed as circuit with the opened circulation of flow and with throttle regulation; a hydraulic drive of moving (an onboard scheme) in the form of two hydraulic transfers with the closed circulation of flow and with volumetric regulation. Thus, the drive as a whole consists of seven functional blocks: the diesel engine, pump station with the opened circulation of flow, two pump stations with the closed circulation of flow, the hydraulic cylinder, two hydraulic motors.

Fig. 11. Simplified circuit and dynamic analysis of an asphalt spreader hydraulic drive.

а – the simplified circuit of an asphalt spreader hydraulic drive, b – results of dynamic analysis

External influences are: a directional control valve spool movement from a neutral position to the working  according to linear law for one second, since the time moment 0.5 s; a change of geometric volumes of pump stations with the closed circulation of flow for one second according to linear law: the first – from zero up to the half of maximal flow, the second – from zero up to a maximum flow; constant loading on the hydraulic cylinder rod (node 10); the constant torque moments on shafts of hydraulic motors (nodes 4 and 7).

On Fig. 11 b results of dynamic calculation are presented: dependences on time of pressure in nodes 2, 3, 5, 6, 8; angular speeds in nodes 4 and 7; linear speed in node 10.