Patent Description:
The disclosure of <CIT> discloses systems for optimizing operation of a marine drive of the type whose position may be varied with respect to the boat by the operation of separate lift and trim/tilt means.

The disclosure of <CIT> discloses a Hall effect rotational position sensor mounted on a pivotable member of a marine propulsion system and a rotatable portion of the rotational position sensor attached to a drive structure of the marine propulsion system. Relative movement between the pivotable member, such as a gimbal ring, and the drive structure, such as the outboard drive portion of the marine propulsion system, cause relative movement between the rotatable and stationary portions of the rotational position sensor. As a result, signals can be provided which are representative of the angular position between the drive structure and the pivotable member.

The disclosure of <CIT> discloses an automatic trim control system that changes the trim angle of a marine propulsion device as a function of the speed of the marine vessel relative to the water in which it is operated.

The disclosures of <CIT>; <CIT>; and <CIT> disclose methods and apparatuses for maneuvering multiple engine marine vessels.

The disclosure of <CIT> discloses systems and methods for controlling trim position of a marine propulsion device on a marine vessel. The system comprises a trim actuator having a first end that is configured to couple to the marine propulsion device and a second end that is configured to couple to the marine vessel. The trim actuator is movable between an extended position wherein the marine propulsion device is trimmed up with respect to the marine vessel and a retracted position wherein the marine propulsion device is trimmed down with respect to the marine vessel. Increasing an amount of voltage to an electromagnet increases the shear strength of a magnetic fluid in the trim actuator thereby restricting movement of the trim actuator into and out of the extended and retracted positions, and decreasing the amount of voltage to the electromagnet decreases the shear strength of the magnetic fluid thereby facilitating movement of the trim actuator into and out of the extended and retracted positions. A controller is configured to adapt the amount of voltage to the electromagnet based upon at least one condition of the system.

The disclosure of <CIT> discloses a method for positioning a drive unit on a marine vessel that includes receiving an initiation request from a user input device to operate the marine vessel in a desired operating mode and storing a first trim position of the drive unit in a memory upon receiving the initiation request. The method includes trimming the drive unit to a second trim position in response to the initiation request and subsequently operating the marine vessel in the desired operating mode with the drive unit in the second trim position. The method includes receiving a termination request to cancel the desired operating mode and trimming the drive unit to the first trim position automatically upon receiving the termination request. A system for positioning the drive unit is also disclosed.

The disclosure of <CIT> discloses a method for controlling a trim system on a marine vessel that includes receiving an actual trim position of a trimmable marine device at a controller and determining a trim position error by comparing the actual trim position to a target trim position with the controller. The method also includes determining an acceleration rate of the marine vessel. In response to determining that the trim position error exceeds a first error threshold and the magnitude of the acceleration rate exceeds a given rate threshold, the controller commands the marine device to the target trim position. In response to determining that the trim position error exceeds the first error threshold and the acceleration rate does not exceed the given rate threshold, the controller commands the marine device to a set point trim position that is different from the target trim position. An associated system is also disclosed.

The disclosure of <CIT> discloses systems and methods for controlling position of a trimmable drive unit with respect to a marine vessel. A controller determines a target trim position as a function of vessel or engine speed. An actual trim position is measured and compared to the target trim position. The controller sends a control signal to a trim actuator to trim the drive unit toward the target trim position if the actual trim position is not equal to the target trim position and if at least one of the following is true: a defined dwell time has elapsed since a previous control signal was sent to the trim actuator to trim the drive unit; a given number of previous control signals has not been exceeded in an attempt to achieve the target trim position; and a difference between the target trim position and the actual trim position is outside of a given deadband.

<CIT> discloses systems and methods for controlling the movement of propulsion units on a marine vessel.

According to an aspect of the present invention, there is provided a method of controlling a marine drive on a marine vessel as claimed in claim <NUM>.

According to another aspect of the present invention, there is provided a system for controlling position of a marine drive on a marine vessel as claimed in claim <NUM>.

According to another aspect of the present invention, there is provided a propulsion system for a marine vessel as claimed in claim <NUM>.

The inventors have recognized that a problem exists with drive collision where, in marine vessels with multiple independently steerable drives (e.g., multiple outboard drives configured for joystick steering), the drives can collide with one another at certain steering and trim positions. The chance for drive collision becomes greater when the drives are mounted close together, such as where several drives are mounted to the transom or where two or more drives are mounted close together at the center of the vessel's stern. Drive collision can damage the propeller, gear case, or other portions of either or both of the colliding drives, and can even leave one or more of the colliding drives inoperable. Thus, avoidance of drive collision is extremely important.

On many current multi-engine vessels, drive collision is avoided by utilizing a mechanical tie bar (such as a collapsible tie bar) or other mechanical link between the drives that prevents the drives from being steered into positions where they might collide with peer drives. These tie bar solutions connect adjacent drives together in such a way so as to physically prevent adjacent drives from moving into positions where they can collide with one another. However, tie bar solutions and other solutions that mechanically link two drives are not workable for drive configurations where the steerable portion of the drive is below the water surface, such as stern drives and or outboard drives with steerable gear cases. In these types of drives, a tie bar or other mechanical link between the steerable drive portions would have to be mounted below the water surface, which would create drag and other unwanted affects and would not be a workable solution. Thus, a solution is needed for preventing drive collision that does not require mechanically linking the marine drives.

Moreover, through their experimentation, research, and experience in the relevant field, the inventors have recognized that drive collision is most likely to happen during trim transition, where the trim angle of one or more of the drives is being adjusted. The risk of drive collision is particularly high during large trim adjustments where one drive is being fully trimmed up to pull it out of the water or is being trimmed down from a fully trimmed up position to put the drive into the water. During these trim transitions, a situation can occur where the steerable portion of the trimmed drive (e.g., that which includes the propeller) impacts a portion of the adjacent drive, such as the cowl, gearcase, cavitation plate, etc. Alternatively, a situation can occur where the gearcase or other portion of the trimmed drive can be lowered onto and impact the propeller or steerable portion of the adjacent drive. These types of impacts can cause severe damage to one or both colliding drives.

In view of the forgoing problems and challenges with drive collision avoidance recognized by the inventors, the disclosed system and method were developed to provide a software solution for avoiding drive collision. In the disclosed system and method, the allowable steering angle range of one or more of the marine drives is limited based on trim position. For example, an allowable steering angle range is defined for various trim positions. The drive steering angle is then automatically controlled to remain within the allowable steering angle range as the drive is trimmed up or trimmed down in response to an instruction to change the trim position of the drive.

In one embodiment, trim position and steering position are adjusted simultaneously so as to force the steerable drive toward a centered steering position as the trim position increases toward a maximum trim position. In certain embodiments, a threshold trim position is set below which a maximum steering angle range is permitted, and thus no limitations are set beyond the normal steering angle limitations set for a multi-drive system. Once the trim position is adjusted above the threshold trim position, the allowable steering angle range narrows around the centered steering position so as to force the marine drive toward the centered position, particularly once the drive has reached a threshold trim position where the propeller is substantially or totally above the water surface. Thereby, the drives are prevented from moving into positions where they can collide with peers because no collision will occur when the drives are in or near the centered steering position.

<FIG> schematically depicts a marine vessel <NUM> having a plurality of marine drives 12a, 12b. In the example, the marine drives 12a, 12b are port and starboard marine drives respectively, and are shown coupled to the stern of the marine vessel <NUM>. In other embodiments, the marine vessel <NUM> may be configured with more than two drives, such as multi-drive systems with three, four, five, or six drives. The marine drives 12a, 12b shown herein are outboard motors, but could alternatively be stern drives. The marine vessel <NUM> further comprises at least one user input device. In the example shown, the at least one user input device comprises a steering wheel <NUM>, throttle lever <NUM>, joystick <NUM>, keypad <NUM>, touchscreen <NUM>, and/or trim control buttons <NUM>. The trim control buttons <NUM> may be a keypad, lever, or any other arrangement configured to facilitate user input to control trim position of the marine drives <NUM>. In other embodiments, the keypad <NUM> and/or touchscreen <NUM> may be configured as user input devices for inputting a trim position instruction to control and adjust trim position of one or more of the marine drives <NUM>. Each of these user input devices is located at a helm <NUM> of the marine vessel <NUM>.

Each of the user input devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is communicatively connected via a controller area network (CAN) bus <NUM> to one or more controllers, such as command control modules (CCMs) 28a, 28b. The CCMs 28a, 28b effectively receive and send all signals from and to the user input devices at the helm <NUM>. In the depicted examples, the CCMs 28a, 28b are communicatively connected via the CAN bus <NUM> to engine control modules (ECMs) 30a, 30b on each marine drive <NUM>. This control system <NUM> arrangement is merely representative and various other arrangements are known and within the scope of the disclosure. For example, each drive may comprise two or more controllers, such as a powertrain control module (PCM) and a thrust vector module (TVM), as is well-known in the art. In other alternative control system <NUM> arrangements, a central control module may be provided in addition to or in place of the CCMs 28a, 28b.

The system <NUM> for positioning marine drives 12a and 12b further includes a trim actuator 48a and 48b and a steering actuator 50a and 50b associated with each drive 12a and 12b. In the depicted example, each CCM 28a and 28b is communicatively connected (e.g., via a CAN bus arrangement) and configured to control the trim actuators <NUM> and steering actuators <NUM>; however, various other control arrangements are possible and well known in the relevant art. The trim actuators 48a, 48b move the marine drives 12a, 12b to a requested trim position, in response to signals sent from the CCMs 28a, 28b, such as based on input from the user input devices (e.g., trim control buttons <NUM>). Further, the control system <NUM> comprises trim angle sensors 35a, 35b for sensing current trim positions of the marine drives 12a, 12b and providing this data to the control modules via the CAN bus <NUM>. The steering actuators 50a, 50b steer the marine drives 12a, 12b in response to signals sent from the CCMs 28a, 28b via the CAN bus <NUM>. Control of the steering actuators 50a and 50b may further be based on steering position sensed by the steering position sensors 55a and 55b configured to sense and actual steering position of the steerable drive portion.

Now referring to <FIG>, various trim positions of the marine drives 12a, 12b will be described. In the example shown in <FIG>, only the starboard marine drive 12b is shown. However, it should be understood that the port marine drive 12a is or may be positioned in the same trim positions as the starboard marine drive 12b shown in these figures, and can therefore not be seen behind the starboard marine drive 12b. It should be understood that in alternative embodiments, the marine vessel <NUM> may be propelled by more than two marine drives. It should also be understood that in other examples, the two marine drives 12a, 12b may have different trim positions from one another.

In each of <FIG> the trim position of the marine drive 12b is shown with respect to a dashed line representing a vertical axis <NUM>. Additionally, another dashed line in each of the figures represents a longitudinal axis <NUM> through the marine drive 12b. The angle between the vertical axis <NUM> and the longitudinal axis <NUM> is the trim angle A. In <FIG>, the marine drive 12b is in a neutral trim position in which the vertical axis <NUM> and the longitudinal axis <NUM> are generally parallel to one another. In <FIG>, the marine drive 12b is trimmed all the way down (trimmed in) such that a propeller <NUM> of the marine drive 12b is closer to a hull <NUM> of the marine vessel <NUM> than when the marine drive 12b is in the neutral trim position. This position is sometimes referred to as "full tuck". In <FIG> the marine drive 12b is trimmed up (trimmed out) such that the propeller <NUM> is further from the hull <NUM>.

In <FIG> the propeller <NUM> of the drive 12b is at or near the water surface. For trim positions at and/or above that point, thrust will not be fully effectuated because the propeller <NUM> will not be fully engaged with the water. Thus, the drive 12b will not be able to fully effectuate steering or thrust commands in that position and trim positions at or above that point are generally undesirable when the drive 12b is engaged in propulsion operations for the vessel. <FIG> is a closer depiction of the drive 12b trimmed up even further, which may represent the drive 12b in a maximum trim position where it is fully trimmed up (or trimmed out) and is lifted out of the water. Marine drives are placed in this position when they are inoperative, such as when they are not needed for low speed steering operations or when a malfunction has occurred with that drive. In this position the drive 12b is lifted out of the water so that it does not create drag and/or so that it is out of the way.

<FIG> depicts the marine drive 12b in a neutral trim position. In the example shown in <FIG>, the trim angle of the marine drive 12b is such that a reverse thrust R provided by the marine drive 12b does not intersect with the hull <NUM> of the marine vessel <NUM> during any rotational orientation of the marine drive 12b about its longitudinal axis <NUM>. Further, the trim angle of the marine drive 12b is such that reverse thrust R is not trimmed too far up away from the vertical axis <NUM> such that the marine drive 12b may still efficiently achieve reverse or rotational movement of the marine vessel <NUM>. In the example of <FIG>, the trim position (shown by longitudinal axis <NUM>) is substantially parallel to the vertical axis <NUM>.

The marine drive 12b can be acutely or obtusely angled with respect to the vertical axis <NUM>. <FIG> shows the marine drive 12b in a trimmed down (trimmed in) position. In the fully trimmed in position, the marine drive 12b is angled such that the propeller <NUM> is closer to the hull <NUM> of the marine vessel <NUM> than when in the neutral position, and its longitudinal axis <NUM> is oriented at an angle A1 with respect to the vertical axis <NUM> (which may be described as a negative angle).

In <FIG>, the marine drive 12b is shown in a trimmed up (trimmed out) position in which the propeller <NUM> is further from the hull <NUM> of the marine vessel <NUM> than when in the neutral position, and the longitudinal axis <NUM> extends at an angle A2 with respect to the vertical axis <NUM>. This provides a reverse thrust R in a somewhat downwardly angled direction as shown and minimal or no forward thrust can be provided because the propeller <NUM> is at or above the water surface; however, when the vessel <NUM> is on plane this drive position may be operable to provide forward thrust. In positions beyond that in <FIG>, such as the maximally trimmed up position at <FIG>, no thrust can be effectuated. To provide just one example, the angle A2 may be around <NUM> degrees of trim, which in various embodiments may be greater or less depending on the vessel configuration, drive configuration, etc..

The trimmed down position shown in <FIG> is a position that is conventionally used during initial forward acceleration (or launch) of the marine vessel <NUM> until full forward translation when the marine vessel <NUM> is on-plane. During such initial forward acceleration, the propeller <NUM> rotates forwardly to provide forward thrust (shown by dashed line F) to propel the marine vessel <NUM> forwardly. When the marine drive 12b is at this trim position for accelerating into forward translation of the marine vessel <NUM>, the marine drive 12b provides forward thrust F that is angled somewhat downwardly.

Once the marine vessel <NUM> is in full forward translation and on-plane, the marine drive 12b is typically trimmed back out of the trim position shown in <FIG>, past the vertical axis <NUM>, and to a slightly raised (trimmed out) trim position (e.g., toward the position in <FIG>). This trimmed up position achieves, for example, optimal speed, riding vessel angle, fuel economy, and/or other desired performance characteristics.

<FIG> depicts a schematic representation of a control system <NUM> that can be used to position the marine drives 12a, 12b on the marine vessel <NUM>. As described hereinabove, the control system <NUM> comprises a throttle lever <NUM>, joystick <NUM>, keypad <NUM>, trim input <NUM> (e.g., trim control buttons), and steering wheel <NUM> (collectively, the user input devices) connected via a CAN bus <NUM> to CCMs 28a, 28b. It should be understood by those having skill in the art that a CAN bus need not be provided, and that these devices could instead be wirelessly connected (or connected by a different communication system) to one another and/or to the CCMs 28a, 28b. Further, the connections shown in dashed lines in both <FIG> and <FIG> are for exemplary purposes only, and may be wired other than as shown herein.

Signals from each of the user input devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are sent via the CAN bus <NUM> to helm controller(s) (in this example CCMs 28a, 28b), which interpret these signals and send commands to the trim actuators 48a and 48b and steering actuators 50a and 50b. In the example shown, the CCMs, PCMs, and TVMs are illustrated as separate modules controlling separate functions aboard the marine vessel <NUM>; however, it should be understood that any of the control sections shown and described herein could be provided in fewer modules or more modules than those shown.

Any of the controllers may have a memory and a programmable processor, such as processor <NUM> and memory <NUM> in CCM 28a. As is conventional, the processor <NUM> can be communicatively connected to a computer readable medium that includes volatile or nonvolatile memory upon which computer readable code (software) is stored. The processor <NUM> can access the computer readable code on the computer readable medium, and upon executing the code can send signals to carry out functions according to the methods described herein below. Execution of the code allows the control system <NUM> to control a series of actuators (for example steering actuators 50a, 50b and trim actuators 48a, 48b) of the marine drives 12a, 12b. Processor <NUM> can be implemented within a single device but can also be distributed across multiple processing devices or sub-systems that cooperate in executing program instructions. Examples include general purpose central processing units, application specific processors, and logic devices, as well as any other type of processing device, combinations of processing devices, and/or variations thereof. The control system <NUM> may also obtain data from sensors aboard the vessel (e.g., trim position sensors 35a and 35b and steering position sensors 55a and 55b, and the processor <NUM> may save or interpret the data as described herein below. In the example shown, at least the port CCM 28a comprises a memory <NUM> (such as, for example, RAM or ROM), although the other control modules could be provided with a memory as well.

Now referring to <FIG>, exemplary methods for positioning the marine drive 12a, 12b on the marine vessel <NUM> are described and shown. <FIG> and <FIG> are graphs illustrating various schemes for setting an allowable steering angle range based on trim. The allowable steering angle range represents the permitted steering angles, and thus the angles at which the drive can be positioned in response to a steering instruction. The allowable steering angles may be symmetrical about the centered steering position, or <NUM> steering angle, which is generally perpendicular to the stern of the vessel <NUM>. The graphs represent allowable steering angle magnitude from the centered steering position, and thus the allowable steering angle range will be the depicted steering angle magnitude on either side of the centered steering position. For instance, the maximum allowed steering angle of <NUM> degrees represents an allowable steering angle range of +<NUM> degrees and -<NUM> degrees with respect to the centered steering position. When the allowable steering angle range is set to the maximum steering range, the drive can be steered to any position within that range <NUM> degree total range, such as based on inputs from the steering wheel <NUM>, joystick <NUM>, etc..

The allowable steering angle range is a maximum steering angle range where no additional constraints are placed on the permitted steering angles beyond those normally in place for steering the drives on the marine vessel. As will be known to a person of ordinary skill in the art, the maximum steering angle range is normally constrained in drive-by-wire applications, for example, based on the range of the steering actuator <NUM>, the mount for the steerable portion of the marine drive <NUM>, the location and arrangement of the marine drives, etc. At the maximum steering angle range, no trim-based constraints are enacted. But as the trim angle increases toward the maximum trim angle, the allowable steering angle range narrows around the centered steering position so as to force the marine drive toward the centered steering position as the marine drive is trimmed up toward the maximum trim position. This may be a gradual centering as the drive is trimmed up. In other embodiments, the drive may be automatically and fully centered when it is raised above a threshold trim position.

Various algorithms and relationships for controlling steering position based on trim may be implemented, examples of which are shown in <FIG> and <FIG>. <FIG> depicts three different exemplary relationships between trim angle and allowable steering angle range. In these examples, the allowed steering angle range progressively narrows around the centered steering position, between a maximum steering angle range at a minimum trim position and a zero steering angle (representing a centered steering position) at a maximum trim position where the marine drive is fully trimmed up and out of the water. In these examples, the minimum trim position is a trim angle of - <NUM> degrees and the maximum trim angle is <NUM> degrees. As will be known to a person having ordinary skill in the art, the values and range between minimum and maximum angles may vary depending on the vessel and drive configurations.

Line <NUM> represents an exponential relationship between allowed steering angle and trim angle where the allowable steering angle range decreases exponentially as the trim angle increases. In the depicted exponential relationship, the allowable steering angle range is at a maximum at low trim angle ranges close to <NUM>, and begins to narrow at about <NUM> degrees of trim. In other embodiments, the allowable steering angle range may remain at the maximum steering angle range for trim positions below a threshold trim position, such as below the first trim position threshold <NUM> illustrated with respect to the modified linear funnel illustrated at line <NUM> and discussed below. The exponential relationship is configured to progressively move the steerable drive to the centered steering position as the trim angle of the drive increases such that the centered steering position is reached at or before the drive reaches the maximum trim position. In the depicted embodiment, the steering angle constraints are configured such that the drive is forced to the centered position as the trim angle reaches a second threshold trim position <NUM>, which is less than the maximum trim position.

The two other lines at <FIG> depict exemplary linear relationships between allowed steering angle range and trim angle. Line <NUM> represents a linear funnel where the allowed steering angle range decreases linearly as the trim angle increases between the minimum trim position where the drive is fully tucked and the second threshold where the drive is at or near the maximum trim position. Line <NUM> represents a second exemplary linear relationship where the steering angle range decreases linearly between a first threshold trim position <NUM> and the second threshold trim position <NUM>. Thus, the allowable steering angle range is the maximum steering angle range of <NUM> degrees at all trim positions below the threshold trim position <NUM>, which in the depicted example is about <NUM> degrees of trim. The allowable steering angle range then progressively narrows as the trim angle increases so as to force the drive into the centered position.

<FIG> represents another embodiment where the relationship between trim and steering angle is a step function. An exemplary step profile is presented by line <NUM>, where a maximum allowable steering angle range is associated with trim positions below the threshold trim position <NUM> and for trim positions above the threshold trim position <NUM>, the allowable steering angle range is the centered steering position. Thus, the steerable drive <NUM> is centered once during the trim up process when the trim angle passes the threshold <NUM>. This arrangement has the benefit of only needing to activate the steering actuator <NUM> once during a trim up routine where the drive is being raised out of the water. In certain embodiments, hysteresis may be implemented to avoid toggling the steering position of the drive if trim is adjusted slightly up or down around the established threshold trim value.

In the example depicted at <FIG>, the threshold trim position <NUM> is <NUM> degrees; however, in various embodiments the threshold trim position can be less than or greater than <NUM> degrees. Preferably, at the threshold trim position <NUM> the propeller <NUM> is at or above the water surface, and thus the drive is not actively steering the marine vessel. Thus, a forced change in steering position will not affect the propulsion vector acted on the marine vessel <NUM>. For example, the threshold trim position <NUM> may be greater than or equal to the trimmed out position depicted at <FIG> where the propeller <NUM> is at the water surface. In other embodiments, the threshold trim position <NUM> may be substantially greater than the angle depicted at <FIG> such that the propeller is well above the water surface before the centering occurs.

The allowable steering angle range is then determined based on trim positions. For example, the relevant controller may store a lookup table providing allowable steering angle range in association with trim angle. The allowable steering angle range may then be determined by utilizing the lookup table, such as based on a current trim angle occupied by the marine drive and sensed by the trim angle sensor <NUM> or based on a target trim position determined based on the trim position instruction provided at the user input device.

<FIG> and <FIG> depict exemplary methods of controlling a marine drive on a marine vessel in order to avoid drive collision during trim position changes, as described herein. In the flowchart at <FIG>, the method <NUM> includes receiving a trim position instruction at step <NUM>, such as from a user input device configured to receive user input to adjust a trim position of the marine drive (e.g., trim control input buttons <NUM>, or any other user input device configured for inputting trim control commands). An allowable steering range is then determined at step <NUM> that accounts for the adjusted trim position based on the trim position instructions. The trim position and steering position are then adjusted accordingly at step <NUM> such that the steering angle of the steerable marine drive remains within the allowable steering angle range. In various embodiments, the allowable steering angle range may be determined based on a trim position occupied by the drive, such as after effectuating the trim position adjustment commanded by the trim position instruction. In other embodiments, the allowable steering angle range may be determined based on the target trim position commanded by the trim position instruction. An example of such an embodiment is depicted at <FIG>.

In the flowchart at <FIG>, the method <NUM> of controlling a marine drive includes receiving a trim position instruction at step <NUM> and then determining a target trim position at step <NUM> based on the trim position instruction. Target trim position determinations based on user inputs at trim control input devices are well known in the relevant art, examples of which are shown and described in <CIT>, which is incorporated herein. Logic is executed at step <NUM> to determine whether the target trim position is greater than a threshold trim position. The target trim position here is a threshold, wherein at trim positions below the threshold steering range is not narrowed based on trim. Thus, if the target trim position is less than the threshold trim position, then no steering adjustment is made as represented at step <NUM>.

In embodiments where the relationship between trim and steering position is a step function, such as exemplified in <FIG>, the threshold trim position utilized at step <NUM> may be the threshold trim position <NUM> representing a position where the propeller <NUM> of the marine drive is at or above the water surface. However, in various embodiments the threshold trim position utilized at step <NUM> may be at a lower trim position, such as the threshold trim position <NUM> represented at <FIG>.

Once the target trim position exceeds the threshold trim position, the allowable steering angle range is narrowed at step <NUM> based on the target trim position. For example, the allowable steering angle range may be determined using a lookup table based on the target trim position. In embodiments where the allowable steering angle range is a step function such as that depicted in <FIG>, the allowable steering angle range will represent the centered steering position. The steering actuator is then controlled at step <NUM> to maintain the steering position within the allowable steering angle range. The trim actuator is controlled to adjust the position of the marine drive to the target trim position at step <NUM>.

Claim 1:
A method of controlling a marine drive (12a, 12b) on a marine vessel (<NUM>), the method comprising:
receiving a trim position instruction to adjust a trim position (<NUM>) of the marine drive (12a, 12b);
determining an allowable steering angle range based on the trim position instruction and/or the adjusted trim position (<NUM>) of the marine drive (12a, 12b); and
controlling a trim actuator (48a, 48b) to adjust the trim position (<NUM>) of the marine drive (12a, 12b) based on the trim position instruction and controlling a steering actuator (50a, 50b) to automatically adjust a steering position of the marine drive (12a, 12b) to remain within the determined allowable steering angle range, characterised in that the trim position (<NUM>) and the steering position are controlled simultaneously based on the trim position instruction so as to avoid collision with an adjacent marine drive (12a, 12b) on the marine vessel (<NUM>) when effectuating the instructed trim position (<NUM>) adjustment.