Multi- engine hydraulic-drive power trowel

Abstract

A ride-on power trowel has first and second engines mounted to a rigid frame. Each of first and second drive loops have a hydraulic pump powered by such an engine and a drive motor powered by the hydraulic pump. Rotor assemblies are coupled to the drive motors and configured to contact a concrete surface beneath the frame. A feedback controller sets rotor speed in each assembly to a power limited speed based on loads sensed in the drive loops. The power limited speed is an estimated maximum rotor speed achievable for the highest sensed load, which may be affected by operating data received from the engine associated with the highest sensed load.

What is claimed is: 
     
         1 . A ride-on power trowel, comprising:
 a rigid frame;   first and second engines mounted to the rigid frame;   a first hydraulic drive loop having a first hydraulic pump powered by the first engine and a first drive motor powered by the first hydraulic pump;   a second hydraulic drive loop having a second hydraulic pump powered by the second engine and a second drive motor powered by the second hydraulic pump;   first and second rotor assemblies coupled respectively to the first and second drive motors and configured to contact a concrete surface beneath the rigid frame;   feedback control means for setting rotor speed in each rotor assembly to a power limited speed.   
     
     
         2 . The trowel of  claim 1 , wherein the feedback control means further comprises:
 a first means for sensing rotor load in the first hydraulic drive loop; and   a second means for sensing rotor load in the second hydraulic drive loop;   wherein the feedback control means sets the rotor speed in each rotor assembly based on the loads sensed in the hydraulic drive loops.   
     
     
         3 . The trowel of  claim 2 , wherein at least one of the first means and the second means comprises a pressure transducer. 
     
     
         4 . The trowel of  claim 2 , wherein at least one of the first means and the second means comprises a torque sensor. 
     
     
         5 . The trowel of  claim 2 , wherein at least one of the first means and the second means comprises a fuel consumption monitor. 
     
     
         6 . The trowel of  claim 2 , wherein at least one of the first means and the second means comprises a CPU configured to receive a signal from an engine control unit associated with one of the first and second engines. 
     
     
         7 . The trowel of  claim 2 , wherein the feedback control means comprises a controller configured to receive from the first means a first load signal representing load in the first hydraulic drive loop and to receive from the second means a second load signal representing load in the second hydraulic drive loop. 
     
     
         8 . The trowel of  claim 7 , wherein the controller is configured to determine a first speed from the first load signal and to determine a second speed from the second load signal. 
     
     
         9 . The trowel of  claim 8 , wherein the controller determines the first speed from the first load signal using a lookup table. 
     
     
         10 . The trowel of  claim 8 , wherein the controller is further configured to determine an operating speed as a lowest value of the first speed and the second speed. 
     
     
         11 . The trowel of  claim 8 , wherein the controller determines an adjustment to an operator desired speed based on one or both of (i) the lowest value of the first speed and the second speed and (ii) engine operating data received by the controller from the first engine or from the second engine. 
     
     
         12 . The trowel of  claim 11 , wherein the engine operating data is received as a CAN bus signal. 
     
     
         13 . The trowel of  claim 1 , wherein the feedback control means includes means for sensing speed of the first drive motor and means for sensing speed of the second drive motor. 
     
     
         14 . A ride-on power trowel, comprising:
 a rigid frame;   a first power train mounted to the rigid frame and comprising a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor;   a second power train mounted to the rigid frame and comprising a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor;   means for sensing a first load on the first hydraulic pump;   means for sensing a second load on the second hydraulic pump; and   control means configured to generate, responsive to receiving the sensed first load and the sensed second load, a control signal causing a change in speed of at least one of the first and second drive motors;   wherein the first and second rotor assemblies are configured to contact a concrete surface beneath the rigid frame.   
     
     
         15 . The trowel of  claim 14 , wherein the generated the control signal is based on a comparison of the sensed first load to the sensed second load. 
     
     
         16 . The trowel of  claim 15 , wherein the generated control signal represents slowest speed between a first optimal speed associated with the sensed first load and a second optimal speed associated with the sensed second load. 
     
     
         17 . The trowel of  claim 14 , wherein the generated control signal causes speed of the first drive motor to be substantially equal to speed of the second drive motor. 
     
     
         18 . A ride-on power trowel, comprising:
 a rigid frame;   a first power train mounted to the rigid frame and comprising a first engine, a first hydraulic pump powered only by the first engine, a first drive motor powered only by the first hydraulic pump, and a first rotor assembly coupled to the first drive motor and configured to contact a concrete surface beneath the frame;   a second power train mounted to the rigid frame and comprising a second engine, a second hydraulic pump powered only by the second engine, a second drive motor powered only by the second hydraulic pump, and a second rotor assembly coupled to the second drive motor and configured to contact the concrete surface beneath the rigid frame; and   a controller mounted to the trowel and programmed limit speed of the first drive motor and speed of the second drive motor to a power limited speed of whichever one of the first drive motor and the second drive motor is under heavier load.   
     
     
         19 . The power trowel of  claim 18 , wherein the controller determines a stroke control command for the first drive motor and for the second drive motor as a function of both feed-forward control and feedback control. 
     
     
         20 . A ride-on power trowel comprising:
 multiple engines, multiple hydraulic motors, and multiple trowel rotors, wherein each of the engines is configured to drive only one of the hydraulic motors, and wherein each of the hydraulic motors is configured to drive only one of the trowel rotors; and   a controller programmed to limit speed of all of the hydraulic motors according to a power limited speed of whichever one of the hydraulic motors is under heaviest load.