Electronic camshaft motor control for piston pump
A two (or more) piston pump system ( 10 ) is provided with both pumps ( 12 ) being crank ( 14 ) driven. The system does not have a mechanical camshaft, but a software algorithm, which acts like one in controller ( 20 ). The algorithm will LEARN and create a unique speed profile, which will mimic the mechanical camshaft. For practical purposes the speed profile of output gear is called Cam profile with software acting as an imaginary camshaft. The algorithm utilizes Crank Angle Estimation, Learn Curve Generation, Smoothing and Advance Timing Calculation.
1. A piston pump system comprising:
at least two crank driven reciprocating pumps, the cranks of said pumps being offset;
an electric motor for driving the said at least two pumps; and
a controller for controlling the operation of said pumps by causing the electric motor to drive the pumps according to a motor speed profile that mimics a mechanical camshaft, wherein the motor speed profile is based upon:
a theoretical cam speed profile for said pumps that takes into account more than one of the parameters of degree of displacement of pistons, volume of the piston rod, change-over duration and geometries of connecting rod and pump bore;
a pump unique profile learned by operating said pump system to produce a learned cam speed profile; and
a practical cam speed profile produced by overlaying said theoretical cam speed profile with said learned cam speed profile.
2. The piston pump system as claimed in claim 1 , wherein the cranks of the said pumps are offset by approximately 84°.
3. A piston pump system comprising:
at least two crank driven reciprocating pumps, cranks of said pumps being offset;
an electric motor for driving the said at least two pumps; and
a controller for controlling operation of the electric motor according to a motor speed profile that mimics a mechanical camshaft, wherein the controller develops the motor speed profile by:
(a) operating said pump system at a constant speed and collecting output pressure data at a selection of crank angle positions;
(b) forming a pressure profile from said output pressure data collection;
(c) inverting said pressure profile to form a motor speed profile which will reduce pressure variation; and
(d) repeating the above steps (a)-(c) at least once in an iterative process until pressure variation does not exceed a predetermined amount.
4. The piston pump system as claimed in claim 3 , wherein the controller is further configured to monitor pressure variation during operation and adjust said motor speed profile to reduce pressure variation in the event said predetermined amount is exceeded.