Patent Grant
9682760
The present disclosure relates to marine propulsion systems for use on marine vessels, and more specifically to systems and methods for setting an engine speed of an internal combustion engine of a marine propulsion system.
U.S. Pat. No. 6,298,824, hereby incorporated by reference herein, discloses a control system for a fuel injected engine including an engine control unit that receives signals from a throttle handle that is manually manipulated by an operator of a marine vessel. The engine control unit also measures engine speed and various other parameters, such as manifold absolute pressure, temperature, barometric pressure, and throttle position. The engine control unit controls the timing of fuel injectors and the injection system and also controls the position of a throttle plate. No direct connection is provided between a manually manipulated throttle handle and the throttle plate. All operating parameters are either calculated as a function of ambient conditions or determined by selecting parameters from matrices which allow the engine control unit to set the operating parameters as a function of engine speed and torque demand, as represented by the position of the throttle handle.
U.S. Pat. No. 8,762,022, hereby incorporated by reference herein, discloses a system and method for efficiently changing controlled engine speed of a marine internal combustion engine in a marine propulsion system for propelling a marine vessel. The system responds to the operator changing the operator-selected engine speed, from a first selected engine speed to a second-selected engine speed, by predicting throttle position needed to provide the second-selected engine speed, and providing a feed forward signal moving the throttle to the predicted throttle position, without waiting for a slower responding PID controller and/or overshoot thereof, and concomitant instability or oscillation, and then uses the engine speed control system including the PID controller to maintain engine speed at the second-selected engine speed.
This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
One example of the present disclosure is of a method for setting an engine speed of an internal combustion engine in a marine propulsion device of a marine propulsion system to an engine speed setpoint. The method includes receiving an operator demand from an input device and learning an adapted maximum engine speed. An engine speed setpoint is calculated by scaling the adapted maximum engine speed relative to the operator demand. The method includes predicting a position of a throttle valve of the engine that is needed to achieve the engine speed setpoint, and determining a feed forward signal that will move the throttle valve to the predicted position.
Another example of the present disclosure is of a marine propulsion system comprising a marine propulsion device, an internal combustion engine powering the marine propulsion device, and a throttle valve metering air intake to the internal combustion engine. The system also includes an input device for inputting an operator demand, and an electronic control unit. The electronic control unit learns an adapted maximum engine speed, calculates an engine speed setpoint by scaling the adapted maximum engine speed relative to the operator demand, predicts a position of the throttle valve that is needed to achieve the engine speed setpoint, and determines a feed forward signal that will move the throttle valve to the predicted position.
The present disclosure is described with reference to the following figures. The same numbers are used throughout the figures to reference like features and like components.
In the present description, certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed.
In response to the operator changing the operator-selected engine speed at input device 20 from a first-selected engine speed to a second-selected engine speed (i.e. a change or delta), the ECU 22 sends a signal to move the throttle valve 32 to a new position to attempt to set the engine speed to the noted second-selected engine speed. However, this type of system is subject to overshoot, particularly at large deltas, when attempting to set engine speed to the second-selected engine speed in response to the noted change by the operator of the selected engine speed at input device 20. To accommodate various deltas, including large deltas, the feedback controller 28 is provided with enough amplification gain to provide a desired response time to accommodate the change from the first-selected engine speed to the second-selected engine speed at input device 20. The higher the amplification gain, the quicker the response time; however, higher gain makes the system subject to more overshoot and instability.
Referring to
Throttle valve 32 is therefore moved to the predicted throttle position in response to the feed forward signal at 34, without waiting for the input of the feedback controller 28 to move the throttle valve 32, thereby decreasing or eliminating any overshoot otherwise caused by the system. The system of
Additionally, by utilizing a method wherein the learned adapted maximum engine speed is taken into account, and scaled relative to the operator demand, it is possible to reduce or eliminate a “dead zone” effect associated with the input device 20. One example of when this effect occurs is when an operator is nearing a full throttle request via the input device 20. Typically, engines are calibrated for operation at a rated maximum engine speed. However, if a marine vessel 14 is propped or loaded such that the maximum speed its engine can actually achieve is less than the rated maximum engine speed, despite what the operator demand may be, the entire load curve of the engine 12 will be shifted vis-à-vis the target nominal case for which the application was calibrated. This load curve shift creates a need for additional throttle to be added based on the difference between the engine speed setpoint and the actual engine speed (i.e. windup), and/or requires limiting output of the feedback controller 28 (more specifically, its integral term) to avoid large offsets. For example, say a non-scaled feed forward signal corresponding to an operator demand of 80% nearly maxes out the actual speed capabilities of the engine 12 (engine RPM) due to the marine vessel 14 being over propped or heavily loaded, or due to other reasons that render the engine 12 unable to achieve its rated maximum speed. If the ECU 22 did not take an actual maximum speed at which the engine 12 is capable of operating into account while calculating the engine speed setpoint, the ECU 22 would allow the engine 12 to operate at its peak speed even though the operator demand is only at 80% according to the input device 20. In other words, 80% operator demand could in fact lead to 100% of the engine's speed capabilities if the actual achievable maximum speed of the engine 12 is not taken into account while determining the engine speed setpoint.
In the above-mentioned instance, wherein the available engine speed is maxed out, if the operator used the input device 20 to increase operator demand from 80% to 100%, the speed of the engine 12 and thus of the marine vessel 14 would not be able to increase. The input device 20 would be in a “dead zone,” in which actuation of the input device 20 does not affect engine speed. If the operator then used the input device 20 to decrease operator demand from 100% to 80%, the operator would experience the same effect in reverse, because the decreased operator demand would not result in decreased engine speed until the input device 20 requested a demand below the exemplary 80% operator demand threshold. Taking the actual achievable maximum engine speed into account (i.e. adapting the maximum engine speed) while determining the engine speed setpoint will therefore help avoid windup of the feedback controller 28, as well as ensure that the system 10 and its response to changes in operator demand at the input device 20 are predictable even when the marine vessel 14 is underpropped or lightly loaded in comparison to the calibrated case.
Now turning to
Similarly, when the handle 40 is moved from the neutral detent position in the direction of arrow 42 to forward detent, the transmission is placed in forward gear and the engine 12 remains at idle speed. From the forward detent position, the handle 40 may be moved further in the direction of arrow 48, to provide engine speeds above the idle speed and forward thrust to the marine vessel. In this range of movement, the transmission is in forward gear, and increasing actuation of the handle 40 in the direction of arrow 48 commands increasing speed of the engine, and thus the propeller 16 and the marine vessel 14, until propping or loading conditions prevent any further speed increase. The position of the handle 40 corresponds to an operator demand and may be measured, as mentioned above, using a potentiometer. For example, the position of the handle 40 may correspond to a percentage of total allowed operator demand, such that when the handle 40 is aligned with its center axis along line 50, this corresponds to 0% operator demand, and when the handle 40 is aligned with its center axis along line 52, this corresponds to 100% operator demand. In the example shown in
Returning to
For example, turning to
Whatever relationship between operator demand and engine speed setpoint has been calibrated into the ECU 22, the engine speed setpoint values defining this relationship can thereafter be normalized to create the curve 56 shown in
Each normalized value is then re-associated with its respective operator demand in order to graph the curve 56. The ECU 22 may then map a desired percentage of available engine speed from the normalized set of values representing a change in desired percentage of available engine speed relative to a given change in the operator demand, for example, using the graph of
Meanwhile, returning to
In order to learn the adapted maximum engine speed, the ECU 22 can read an actual maximum engine speed, for example using a tachometer as shown at box 60. This actual maximum engine speed can thereafter be saved in the memory of the ECU 22 as the adapted maximum engine speed that is available given the loading and propping conditions of the marine propulsion system 10. However, in order to ensure that the ECU 22 is reading and saving the actual maximum engine speed (i.e. to avoid learning an incorrect, less-than-maximum engine speed) several criteria may be required to be met before the adapted max engine speed can be learned. For example, the ECU 22 may learn the adapted maximum engine speed only when a measured speed of the engine 12 exceeds a certain speed. In one example, the certain speed could be 4700 RPM, although other speeds could be programmed into the ECU 22. Additionally or alternatively, the adapted maximum engine speed may be learned only when the position of the throttle valve 32 is within a certain range of wide open throttle. For example, the adapted maximum engine speed may only be learned when the throttle position is at 100% (wide open throttle), within 5% of wide open throttle, or within another certain programmed range of wide open throttle. The throttle position can be measured, for example, using a throttle position sensor, as shown at box 62. Additionally or alternatively, the adapted maximum engine speed may be learned only when the operator demand exceeds a certain demand. For example, the adapted maximum engine speed may be learned only when the input device 20 requests a demand at box 36 that is greater than 95%, greater than 98%, or greater than another programmed value.
Additionally or alternatively, the adapted maximum engine speed may be learned only when at least one of the following other conditions is present: a trim angle of the marine propulsion device 11 exceeds a certain angle, and a load on the engine 12 exceeds a certain load. The trim position may be measured at box 64 using a trim position sensor. As an example, the trim position may be required to be at maximum trim (or within a certain angle of maximum trim) before the adapted maximum engine speed will be learned. The load on the engine 12 may be calculated based on measured conditions such as air flow, fueling, intake air temperature, spark timing, manifold air pressure, or any combination of these conditions. For example, the engine load may be required to be above a certain load, or an air flow may be required to be above a certain air flow, before the adapted maximum engine speed will be learned. Sensors for these types of values, such as a MAF sensor, MAP sensor, IAT sensor, etc. may send their measurements over line 66 to box 58. At box 58, the ECU 22 may perform a load calculation using these measured values, and may perform a conjunctive analysis of any of the other above-mentioned enable criteria programmed into its memory, in order to determine whether the engine speed read at box 60 should be saved as the adapted maximum engine speed.
Each of the enable criteria mentioned above (engine speed, throttle lever position, trim sensor position, throttle valve position, and engine load) may be required to be met before the ECU 22 will learn the adapted maximum engine speed. Alternatively, different combinations of these enable criteria may be required to be met in order for the ECU 22 to learn the adapted maximum engine speed. In any case, enough enable criteria should be used to determine that the engine 12 is actually operating at its maximum speed, as the enable criteria are chosen to reflect the most efficient operating conditions of the vessel and to provide redundancy of measurements. If the required criteria are in fact met, the actual engine speed is read as shown at box 60, and this value is provided to box 58 as the adapted maximum engine speed. The adapted maximum engine speed is thereafter sent to box 68 for calculation of the engine speed setpoint, as will be described further herein below.
At box 68, the ECU 22 calculates the engine speed setpoint after it has been provided with the desired percentage of available engine speed from box 54 (determined by using the graph shown in
engine speed setpoint=((adapted max speed−idle)*percent desired speed)+idle Eq. 2.0:
By performing this calculation, the ECU 22 can affect the throttle feel of the input device 20 (e.g. the throttle handle 40). For example, a change in engine speed will result from the entire path of movement of the throttle handle 40 from 0% operator demand at the forward detent position, to 100% operator demand when the handle 40 is aligned with line 52. In other words, the dead zone effect mentioned above will be eliminated, even when the engine 12 cannot achieve the rated maximum engine speed. The method of the present disclosure effectively translates the operator demand input at the input device 20 into a percentage of available engine operating speed. The engine speed setpoint that is used to look up the feed forward signal can then be calculated by using equation 2.0 provided above, and will range from the idle speed to the adapted maximum engine speed (rather than to the rated maximum speed, if the rated speed is unachievable).
engine speed setpoint=((4800−600)*0.8)+600=3960 RPM Eq. 2.1:
However, if the system 10 were set up (loaded and propped) such that the rated engine speed at point 82 was able to be achieved, an operator demand of 71% would instead correspond to an engine speed setpoint of about 4440 RPM, as shown at point 92:
engine speed setpoint=((5400−600)*0.8)+600=4440 RPM Eq. 2.2:
In other words, the method of the present disclosure shifts the entire engine speed response curve down from the curve shown at 78 to the curve shown at 86 due to the fact that the adapted maximum engine speed at point 88 is less than the rated maximum engine speed at point 82. This ensures that the operator feels a difference (increase) in engine speed as he moves the handle 40 of the throttle lever 35 all the way to a 100% demand request. If the maximum engine speed were only 4800 RPM, but the system was not adapted according to the method described herein, then the operator would reach peak engine speed at a position of the handle 40 corresponding to about 78% of its available travel (see dashed line 98), and any movement of the handle 40 between 78% and 100% of its travel would not cause a change in engine speed.
Returning to
What constitutes a “driving cycle” could be defined during programming of the system. In one example, a driving cycle corresponds to each key cycle, i.e. when the engine is turned on after having been off. In another example, a driving cycle is defined as each time the adaptation routine becomes active within a key cycle, based on fulfillment of the enable criteria mentioned above. In yet another example, a driving cycle is defined by a change in measured coolant temperature, such as a change from a relatively higher temperature to a relatively lower temperature of greater than a certain temperature value, or of greater than a certain percent, or as defined by the manufacturer during programming of the system. The amount by which the adapted maximum engine speed changes during each driving cycle, however defined, may be limited so as to provide gradual adaptation that is undetectable from the standpoint of the operator. For example, the increments by which the adapted maximum engine speed is changed would be programmed to be small enough such that the operator does not feel an abrupt change in engine speed or in throttle feel as the adaptation occurs. If the actual measured maximum engine speed is much less than the rated maximum engine speed, the system may chose to adapt in larger increments than if the adapted and rated engine speeds are close to one another, but these increments may still be programmed small enough that the change is undetectable to the operator.
Returning to
As shown at box 60, the actual engine speed is measured, again for example using a tachometer, and this value is provided to the first summer 70. The first summer 70 compares the engine speed setpoint from box 68 with the actual engine speed from box 60, and a difference between the two is sent to the feedback controller 28. As shown at box 76, the feedback controller 28 generates a PID output on the feedback regarding the engine speed setpoint versus the actual engine speed. The PID output from box 76 is summed with the feed forward signal 34 from box 72 at second summer 74, and this summed signal now dictates the position of the throttle valve 32, as shown at box 62. In this way, if the predicted position of the throttle valve 32 (based solely on feed forward signal 34) has not resulted in the actual engine speed reaching the engine speed setpoint, the feedback controller 28 can adjust the position of the throttle valve 32 to obtain the engine speed setpoint. The predicted position of the throttle valve 32 might not result in the setpoint immediately due to the inexactness of a calibrated predicted throttle position, or due to external conditions acting on the marine propulsion system 10 that cause the vessel speed not to follow the standard calibrated speed versus load curve, such as a heavy load on the system 10, an age of the engine 12, a barometric pressure of the surrounding atmosphere, characteristics of the propeller 16, or any other condition that consistently affects the ability of the predicted throttle position as calibrated to achieve a particular engine speed. Under steady-state conditions, the feedback controller 28 is able to stabilize the system 10 at the engine speed setpoint, which may require some iteration of movement of the throttle valve 32 and subsequent comparison of the resulting actual engine speed to the setpoint. The feedback controller 28 also continues to work to maintain the engine speed at the engine speed setpoint despite changing external circumstances or conditions.
Turning to
Next, at box 806, the method may include calculating an engine speed setpoint by scaling the adapted maximum engine speed relative to the operator demand. This may be done by mapping the operator demand to a desired percentage of available engine speed, wherein the desired percentage of available engine speed is mapped from a normalized set of values representing a change in the desired percentage of available engine speed relative to a given change in the operator demand, as described above with respect to
engine speed setpoint=((adapted max. speed−idle)*percent desired speed)+idle Eq. 2.0:
As shown box 808, the method may next include predicting a position of a throttle valve 32 of the engine 12 that is needed to achieve the engine speed setpoint. The method may then include determining a feed forward signal 34 that move the throttle valve 32 to the predicted position, as shown at 810 and as further described with respect to box 72 in
The above-mentioned system and method can be used to improve functions of a marine vessel while it operates in modes such as auto sync and cruise control. In auto sync mode, the speed of a first internal combustion engine (the “peer” engine) is synchronized to the speed of a second internal combustion engine (the “master” engine) of the marine propulsion system 10. If the target speeds of both master and peer engines are normalized such that each can only reach its adapted maximum engine speed, less adjustment may be needed to bring the peer engine to the speed of the master engine if their adapted maximum engine speeds vary (for example, if the peer marine propulsion device is trimmed differently than the master marine propulsion device). In cruise control mode, all engines are provided with the same setpoint speed. If this setpoint speed is set to the lowest adapted maximum engine speed of all the engines, then all engines will be able to reach this adapted maximum speed.
In the above description, certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different systems and method steps described herein may be used alone or in combination with other systems and methods. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims.
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