Patent Application
20110079168
The subject matter disclosed herein relates to a method and system for controlling a lift mechanism in a vehicle.
Vehicles, such as diesel-electric locomotives, may be configured with truck assemblies including two trucks per assembly, and three axles per truck. The three axles may include at least one powered axle and at least one non-powered axle. The axles may be mounted to the truck via lift mechanisms (such as, suspension assemblies including one or more springs) for adjusting a distribution of locomotive weight (including a locomotive body weight and a locomotive truck weight) between the axles. Weight distribution among the powered and non-powered axles may be performed statically and/or dynamically by adjusting a lift command. Under some operating conditions, while the commanded lift may be technically achievable, it may however adversely affect the locomotive or rail or other infrastructure. For example, a lift commanded in the presence of vehicle friction braking may lead to increased stress on locomotive components such as the brake linkage or the wheels and axles, thereby reducing the useful life of the components and reducing the performance of the system. Similarly, a lift commanded in response to wheel slip but before an effective locomotive sanding operation may be unnecessary. As such, this may lead to potential issues arising from the additional stress generated on the slipping axle, slipping wheel, and lift mechanism components.
Systems and methods for a vehicle having a truck with a plurality of axles and a lift mechanism configured to dynamically transfer weight from one axle to another are provided. The method may comprise responding to an operating condition by adjusting the lift mechanism to provide a determined amount of lift; and in response to other dynamic factors, such as locomotive stress conditions, stall risks, infrastructure conditions, and/or vehicle braking, further adjusting the determined amount of lift. In one embodiment, the method comprises responding to an operating condition by adjusting the lift mechanism to provide a determined amount of lift, and in response to vehicle braking, reducing the determined amount of lift. In another embodiment, the method comprises, in response to the identification of a vehicle stall risk, increasing the determined amount of lift. In still another embodiment, the method comprises, in response to an infrastructure condition, reducing the determined amount of lift. In yet another embodiment, the method comprises limiting the determined amount of lift based on a determined vehicle penalty.
In this way, it may be possible to provide lift command adjustments that account for the above interactions and thereby better control dynamic vehicle weight redistribution while achieving high system component life.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:
Vehicles, such as locomotives, may be configured with truck assemblies including lift mechanisms (such as, suspension systems) for transferring weight among wheels and/or axles supporting the locomotive. One example of such a mechanism is illustrated with reference to
As illustrated with reference to
In this way, by adjusting the amount of lift commanded to a locomotive lift mechanism, the tractive force and weight applied on the rail may be adjusted dynamically responsive to locomotive operating conditions. By dynamically redistributing the locomotive load between powered and unpowered axles, it may be possible to reduce the stress of the lift mechanism during increased traction. Likewise, it may be possible to operate the lift mechanism with a more even loading of the axles to provide a smoother ride and reduce frame and rail stresses at higher vehicle speeds. By further reducing the lift command during operating conditions (such as during air braking), where the commanded lift may degrade locomotive operation (for example, by increasing stress on locomotive components, by reducing air brake effectiveness, by increasing wheel slide, etc.), the useful life of the locomotive components may be increased.
As illustrated in the example embodiment of
Each truck 26, 28 may include a pair of spaced apart powered axles 30, 34, 36, 40 and a non-powered axle 32, 38 positioned between the pair of spaced apart powered axles. The powered axles 30, 34, 36, 40 are each respectively coupled to a traction motor 44 and a gear 46. Although
Each of the powered axles 30, 34, 36, and 40 include a suspension 90, and each of the non-powered axles 32 and 38 include a suspension 92. The suspensions may include various elastic and/or damping members, such as compression springs, leaf springs, coil springs, etc. In the depicted example, the non-powered axles 32, 38 may include a DWM actuator (not shown) configured to dynamically adjust a compression of the non-powered axle suspensions by exerting an internal compression force (as described with regard to
Returning to
A vehicle operator may control the operation of the locomotive by adjusting parameters input into a locomotive controller 12. For example, the vehicle operator may control the power output of the locomotive (thereby also controlling locomotive speed) by adjusting a throttle setting. The locomotive may be configured with a stepped or “notched” throttle (not shown) with multiple throttle positions or “notches”. In one example, the throttle may have nine distinct positions, including an idle notch corresponding to an idle engine operation and eight power notches corresponding to powered engine operation. Additionally, an emergency air brake application corresponding to an emergency stop position may also be included. When in the idle notch position, engine 56 may receive a minimal amount of fuel enabling it to idle at low at RPM. Additionally, the traction motors may not be energized. For example, the locomotive may be in a “neutral” state. To commence operation of the locomotive, the operator may select a direction of travel (herein, also referred to as a direction call) by adjusting the position of a reverser 14. As such, the reverser may be placed in a forward, reverse, or neutral position. Upon placing the reverser in either a forward or reverse direction, the operator may release a brake and move the throttle to the first power notch to energize the traction motors. As the throttle is moved to higher power notches, the fuel rate to the engine is increased, resulting in a corresponding increase in the power output and locomotive speed. In one example, as depicted, controller 12, reverser 14, and a vehicle operator may be positioned in cab 16 during locomotive operation.
Traction motor 44 may act as a generator providing dynamic braking to brake locomotive 18. In particular, during dynamic braking, the traction motor may provide torque in a direction that is opposite from the rolling direction thereby generating electricity that is dissipated as heat by a grid of resistors (not shown) connected to the electrical bus. In one example, the grid includes stacks of resistive elements connected in series directly to the electrical bus. Air brakes (not shown) making use of compressed air may be used by locomotive 18 as part of a vehicle braking system.
As noted above, to increase the traction of driven axles of the truck (by effecting a weight shift dynamically from at least one axle of the truck to at least another axle of the truck), one embodiment uses pneumatically actuated relative displacement between the un-powered axle (e.g., 32 and/or 38) and the truck frame element 60. The relative displacement of the un-powered axle causes a change (e.g., compression) of the axle suspension 92, thus causing a shift of weight to the powered axles (and additional compression of the suspension 90) to compensate for the reduced normal force 72 at the un-powered axle. This action generates an increased normal force 70, 74 on the powered axles 30, 34, for example.
Referring now to
In some examples, portions of the weight supported by each carrier 202, 204, 206, and consequently the upward normal forces 70, 72, 74, on each of the wheels 20 may be selectively, and in some examples, dynamically, redistributed among the carriers 202, 204, 206. In some examples, the weight may be redistributed via a weight transference configured to decrease the weight on the non-powered axle 32, thereby increasing the weight on the powered axle 30, 34 and consequently the tractive effort of the locomotive 18 via a corresponding increase in the normal forces 70, 74 on the powered wheels. Truck 28 may also be similarly constructed such that the weight on the non-powered axle 38 may be decreased, increasing the weight on the powered axles 36, 40 and consequently the tractive effort of locomotive 18.
Various actuating arrangements may be employed to reduce the weight on the non-powered axle 32. For example, a pair of actuators 226, 228 may be coupled with the truck frame element 60. A first actuator 226 may be coupled to, or near, a top surface 252 of the truck frame element 60, and a second actuator 228 may be coupled to, or near, a lower surface 254 of the truck frame element 60. The actuators may be configured to share the actuating load for actuating a linkage arrangement 230. Specifically, the actuators may each generate forces in opposite directions, yet offset from one another, to generate a coupling torque that rotates a cam or lever arm to generate lifting force on carrier 204 to displace it relative to, and toward, truck frame element 60. Mechanical advantage may be used by the linkage arrangement to amplify the force from the actuators, and in some examples the mechanical advantage may vary depending on the position of the linkage arrangement. In one example, the actuators 226, 228 may be pneumatic actuators (as elaborated in
The actuatable linkage arrangement 230 includes a compliant linkage coupled with the carrier 204 to translate rotation of a lever arm 214 by the pneumatic actuator-generated couple into vertical motion of the carrier 204 relative to the truck frame element 60. Lever arm 214 may be coupled with a crank (not shown) and may be configured to effect the pivoting of the crank. The two actuators 226, 228 may be configured to exert forces from respectively opposite directions to exert a couple on the lever arm 214. In one example, the compliant linkage may include a chain. In alternate examples, the linkage may include a cable, a strap, a rope, slotted rigid members, or the like. The chain may be able to operate in tension (hereafter referred to as a truck chain tension) to support a load at least an order of magnitude, and often two or more orders of magnitude, greater than that in compression. By enabling the compliant linkage to pull the carrier against the bias in a first direction, it is possible to selectively control increased compression of the carrier toward the truck frame element to effect a dynamic re-distribution of the load to other axles of the truck assembly.
Spring system 210 may include one or more springs 250 configured to couple the axle to the truck frame element 60. While
In one example embodiment, spring system 208 may be configured to provide a non-linear spring rate in response to a deflection between powered axles 30 and 34 and truck frame element 60. In alternate embodiments, spring system 208 may be linear and may provide a spring rate substantially similar to that of spring system 210.
Now turning to
The pressure regulator may be coupled to side cylinder 310 along pneumatic line 301 via a dump valve 306. In one example, dump valve 306 may be an electromagnetic dump valve alternating between an open position 309 and a closed position 307. Specifically, dump valve 306 may remain in a default closed position 307 until enabled or activated by the passage of an electric current, at which time dump valve may shift to the open position 309. In response to a “dump” command, controller 12 may enable the dump valve and the pressure in pneumatic line 301 may be “dumped” to the atmosphere, rapidly and almost instantaneously bringing the air pressure in the line down, for example down to a range of 0-5 psi. In this way, a quick deactivation of the lift mechanism may be provided, for example, in response to a sudden application of friction brakes during an emergency air brake event. Thus, a more rapid lift reduction may be achieved to thereby reduce sliding of the axle. A controlled deactivation of the DWM mechanism may be used during a de-lift operation (e.g., during an operation wherein the locomotive is changed from operating with lift to operating with no lift, or less lift). It will be appreciated that while the figure depicts a single side cylinder communicating with a single spring of the spring system, a similar command may be given in parallel to another side cylinder communicating with the second spring of the spring system.
During a DWM lift operation, dump valve 306 may remain closed and pressure regulator valve 304 may generate a pressure in the pneumatic line 301 based on the commanded pressure. A pressure sensor 308 may monitor the pressure (Pcyl) in the line. The commanded pressure may be transferred to side cylinder 310. The movement of side cylinder 310 may then be relayed to and transformed into a corresponding lift in spring system 210. In one example, when an increase in lift is commanded (herein also referred to as a DWM lift), the movement of side cylinder 310 may enable springs 250 of spring system 210 to decrease their compression rate, thereby bringing carrier 204 closer to truck frame element 60. In another example, when a decrease in lift is commanded (or when a DWM de-lift is commanded), the movement of side cylinder 310 may enable springs 250 of spring system 210 to increase their compression rate, thereby pushing carrier 204 further from truck frame element 60. The controller, when performing DWM control, is responsible for the air pressure on the DWM pneumatic cylinders, which in turn shift weight from non-powered to powered axles on the locomotive. In one example, a push mechanism is used to perform the DWM lift under some conditions and an alternate mechanism (such as a pull mechanism) is used to perform a DWM de-lift under different conditions.
In an alternate embodiment, dump valve 306 may be an electromagnetic valve. Herein, the electromagnetic dump valve may be charged to hold a determined cylinder pressure with or without pressure feedback.
The controller may be configured to adjust the lift mechanism to reduce lift by opening a (first) dump valve during a first operating condition, and reduce lift by opening a (second) regulator valve during a second operating condition. As such, the dump valve may allow for a faster reduction in lift. For example, during a vehicle friction braking condition, the controller may reduce lift (for example, completely reduce lift to a zero lift state) by opening the dump valve. In comparison, during a condition where the vehicle is moving into a low gradient zone (from a high gradient zone), the controller may more slowly reduce lift (for example, slightly reduce lift to a decreased lift state) by opening the regulator valve 304.
Referring now to the control operation as illustrated in
Now turning to
At 401, vehicle operating conditions may be estimated and/or measured. These may include estimating environmental conditions external to the vehicle, such as an ambient temperature, pressure, humidity, weather conditions, etc. A rail track condition (or quality of the track on which the vehicle travels) and a geographical input of the location along the rail track may be determined, for example based on information from a global positioning system (GPS) and/or from a track database. Operator inputs such as a requested notch, a reverser position (e.g., a direction call), and a desired torque (for example, from a throttle position) may be determined. Further still, a fuel amount may be determined based on a fuel tank sensor. The number of locomotives and cabs in the locomotive consist may be determined. Further still, it may be determined whether the locomotive is in a short hood or long hood direction (e.g., whether the short hood or the long hood is forward in the direction of travel), and a direction of travel. Similarly, various other vehicle operating conditions may also be determined.
At 402, it may be determined whether any dump conditions are present. As such, the dump conditions may correspond to vehicle operating conditions and/or locomotive component conditions under which the performance (or maintenance) of a lift operation and the redistribution of weight may adversely affect the vehicle performance and/or the operating condition of locomotive components (for example, by increasing axle sliding and slip). These conditions wherein a lift may not be desired may include, for example, emergency air brake application conditions. Thus, under such dump conditions, even if a lift could be performed, the lift operation may be over-ridden and a dump operation may be performed instead at 404. As such, this may represent a failure mode (or emergency mode) of the control system wherein locomotive degradation due to a lift command may be anticipated and accordingly some or all of the lift may be “dumped”. Further details of an example dump operation are provided herein with reference to
If no dump conditions are identified at 402, then at 406, lift conditions may be confirmed. For example, it may be confirmed whether the vehicle operating conditions permit a lift operation. As further elaborated with reference to
The routine may also be configured to limit or restrict an amount of lift, and thus an amount of weight transfer between axles, based on operating conditions such as the location of the locomotive and/or infrastructure conditions, such as rail conditions. For example, if a specific section of rail can only support limited weight (for example, due to degraded rail quality in a particular section), when that section is reached, the lift operation may be limited. In one example, this may be achieved with the help of a geo-sensing system. The geo-sensing system may include a track database including information regarding the quality, grade, current condition, etc. of tracks along the route the locomotive is expected to travel. The system may also include information regarding the presence of bridges, and the condition of the bridges, the presence of ballasts, the condition of ballasts, etc. Predetermined geographic zones may be stored on an on-board control system (OBS) of the locomotive and may include a location determination system, such as a global positioning system (GPS). In one example, the predetermined geographic zones may be set up as “non-permissible zones”, such that when the locomotive is approaching and/or transitioning through those zones, a weight shift operation is prevented. Alternatively, the predetermined geographic zones may be set up as “permissible zones”, such that when the locomotive is approaching and/or transitioning through those zones, a weight shift operation is enabled. The geographic zone restrictions may be implemented automatically or using manual inputs, such as by the operator enabling a switch or providing authorization from off-board the system using communications. In one example, such geographic zone-based weight transfer restrictions may be enforced alongside dump conditions and/or lift conditions, or may be enforced as limits on the lift command (for example, by assigning a zone-based maximum weight, maximum weight transfer, zone-based truck restriction, zone-based axle restriction, zone-based locomotive position restriction, etc.). In this way, by adjusting the weight transfer operation in an infrastructure-sensitive manner, detrimental track forces may be reduced and ride quality may be improved.
If no lift conditions are confirmed at 406, e.g., if the locomotive is in a state of starting with no lift or running with no lift, the routine may move to 417 and ramp down the air pressure in the lift mechanism actuators (herein also referred to as lifters). For example, the air pressure in the lifters may be gradually reduced towards 0 psi (for example, by bringing it down to 5 psi) to avoid a lift. In one example, a controller may adjust the operation of an electro-pneumatic pressure regulator valve to gradually ramp down the pressure in the lifters. In another example the controller may command a valve to slow bleed the air down. If the air pressure has not reduced after a threshold time since the ramp down was initiated (for example, after 60 secs), the controller may enable the dump valves and rapidly reduce the air pressure towards 0 psi. In comparison, if lift conditions are confirmed at 406, e.g., if the locomotive is in a state of starting with lift or running with lift, the routine may move to 407 and close any dump valves that are not restricted. Additionally, the average air pressure in the lift mechanism may be increased to increase the authority of DWM lift operations.
Next, at 408, the routine may determine a lift condition operating area based upon a map, such as the example map of
Based at least on the position of the locomotive in the lift condition map, and further based on parameters such as the risk of a vehicle stall, the presence of wheel slip, the gradient and state of the track, the vehicle operating conditions, etc., a lift command may be determined at 410. As further elaborated with reference to
At 412, based on the determined lift command, the lift operation may be performed. As such, this may include converting the lift command into an appropriate pressure command that is then relayed to the lift mechanism actuators. In this way, the lift mechanism may be adjusted responsive to various operating conditions to provide the determined amount of lift.
Now turning to
At 502, it may be determined whether there are any emergency conditions. In one example, the emergency conditions may include the detection and/or prediction of undesirable amounts of unpowered axle wheel slide or negative creep. In another example, the emergency conditions may include the sudden application of emergency air brakes (or friction brakes). If emergency conditions are confirmed, at 508 the routine may enable both the dump valves of the suspension system to thereby provide substantially no lift. As previously elaborated, by enabling both the dump valves, the air pressure in the pneumatic line of the lift actuators may be rapidly reduced, thereby quickly deactivating the lift operation.
If no emergency conditions are identified at 502, at 504 it may be determined whether the vehicle is in a braking mode. For example, it may be determined whether the brake cylinder pressure (BC pressure) is greater than a threshold (dwm_max_air_psi), for example above 30 psi, and whether the vehicle speed (ref_spd_abs) is greater than a threshold (dwm_max_air_psi_spd), for example above 5 mph. In response to vehicle braking, the determined amount of lift may be reduced. For example, as illustrated herein, reducing the lift may include providing no lift by opening a dump valve of the lift mechanism. Specifically, if the braking conditions are confirmed at 504, then the routine may proceed to 508 and enable the dump valves of the lift mechanism, thereby disabling lift. In this way, an amount of lift may be rapidly disabled in response to vehicle air braking, thereby reducing unpowered axle slide risk.
In still other examples, instead of dumping the actuation pressure, a controller may sequentially open a regulator valve and a dump valve based on vehicle operating conditions. For example, during a first operating condition, the controller may open a first dump valve to reduce lift. In another example, during a second operation condition, the controller may open a second regulator valve (such as pressure regulator valve 304 of
As such, the conditions depicted at 502-504 represent example dump conditions that may be queried as part of and at the beginning of the lift determination routine 400 (at 402). It will be appreciated that additional or alternate dump conditions may also be confirmed in the dump operation of
Now turning to
The state diagram determines a running state of the locomotive. In the depicted example, the locomotive may be in one of four running states including running with or without lift and starting with or without lift. Following a powering up of the locomotive, the locomotive may initially be in a state of starting with no lift (starting_no_lift 602). From here, the locomotive may either be transitioned to a state of starting with lift (starting_lift 606) or a state of running with no lift (running_no_lift 614). The locomotive may enter starting_lift 606 from starting_no_lift 602 in response to conditions 604 including, the locomotive notch being above a threshold value (dwm_trs_slift_enter_notch), for example, above notch 3, the locomotive being in a motoring condition, the locomotive speed being below a threshold speed (dwm_trs_min_spd), for example, below 3 mph, when at least one truck of the locomotive is unrestricted, and the locomotive is started on a hill. In the presence of conditions 604, a controller may start the locomotive with the lift mechanism activated and with at least some lift in place. In one example, once conditions 604 for a transition are satisfied, a timer may be started and upon the elapse of a threshold time (dwm_trs_slift_tm), for example 5 seconds, the transition may be completed. Additionally, a controller may note the direction of locomotive movement (dir_call), for example as determined by a reverser position. The locomotive may return from starting_lift 606 to starting_no_lift 602 in response to conditions 616 including, the locomotive not being motored, the locomotive notch being below a threshold notch (dwm_trs_slift_exit_notch), for example notch 3, or when both trucks of the locomotive are restricted.
Alternatively, the locomotive may enter the state running_no_lift 614 from the starting_no_lift 602 in response to conditions 618 including the locomotive speed being above a threshold speed (dwm_trs_min_spd), for example, above 3 mph. The locomotive may return from running_no_lift 614 to starting_no_lift 602 in response to conditions 620 including the locomotive speed being below a threshold speed (dwm_trs_slift_exit_spd), for example below 3 mph.
For the locomotive to transition from starting_lift 606 to running_no_lift 614, it may be required to transition through a state of running with lift (running_lift 610). The locomotive may enter running_lift 610 from starting_lift 606 in response to conditions 608 including the locomotive speed being above a threshold speed (dwm_trs_slift_exit_spd), for example, above 5 mph, the locomotive being in a motoring condition, and when at least one truck is not restricted. As such, the locomotive may not be able to return to the state of starting_lift 606 from the state of running_lift 610 without transitioning successively through the states of running_no_lift 614 and starting_no_lift 602.
The locomotive may enter running_no_lift 614 from running_lift 610 in response to conditions 612 including the locomotive speed being above a threshold speed (dwm_trs_rlift_exit_spd), for example, above 18 mph, when both trucks are restricted, the locomotive is in a non-motoring condition, or when a threshold time (dwm_trs_rlift_exit_tm) has elapsed on a timer, for example, 2 hours. Additionally, the controller may ensure that the direction of locomotive movement is not the direction called by the operator (dir_call). The locomotive may return from running_no_lift 614 to running_lift 610 in response to conditions 622 including the locomotive speed being below a threshold speed (dwm_trs_rlift_enter_spd), for example, below 17 mph, when at least one truck is not restricted, the locomotive being in a motoring condition, and the locomotive notch being above a threshold value (dwm_trs_rlift_enter_notch), for example, above notch 8.
When the locomotive is in a condition with lift, e.g., in starting_lift 606 or running_lift 610, the control system may increase the air pressure in the main air reservoir by way of the air compressor. This is done in order to provide adequate system air pressure of the weight shift mechanism actuators. A controller may command the air pressure to be maintained above a minimum threshold pressure, for example, above 135 psi. Additionally, when the locomotive is in the state of running_lift 610, and the locomotive speed is below a threshold speed (dwm_trs_rlift_stop_spd), for example, below 0.1 mph, the threshold time (dwm_trs_rlift_exit_tm) required to transition the locomotive to running_no_lift 414 may be incremented, for example, incremented beyond 2 hrs, to try to provide the desired lift. If however no lift can be provided after the elapse of the threshold time, the timer may be reset. By increasing the average system air pressure upon activation of the DWM mechanism, a higher authority may be provided to the lift operation.
Now turning to
As depicted, map 700 may be represented in terms of locomotive speed and a net tractive effort. Based at least on the locomotive speed and/or the net tractive effort available, the controller may position the locomotive in one of eight operating areas 701-708. Based on the operating area, a corresponding lift option may be determined, for example using a look-up table such as table 710. Using map 700 and table 710, an amount of lift (e.g., the lift command) may be adjusted based on the available tractive effort of the vehicle.
The locomotive may be positioned in a first operating area 701 when the locomotive speed is below a first threshold (for example below 10 mph), and the tractive effort is below a first threshold (for example below 105 klbs). As depicted in table 710, when located in operating area 701, the lift options available are hold (hold the amount of lift present), lift-start (start with lift), lift-run (run with lift), and lift-stall (lift provided in the event of a potential vehicle stall).
The locomotive may be positioned in a second operating area 702 when the locomotive speed is below the first threshold (for example, below 10 mph) and the tractive effort is above the first threshold but below a second threshold (for example above 105 klbs but below 130 klbs). When located in operating area 702, the lift options available are hold, lift-start, lift-run, and lift-min (operate with a minimum amount of lift). The locomotive may be positioned in a third operating area 703 when the locomotive speed is above a second threshold but below the first threshold (for example, above 3 mph but below 10 mph). Additionally, the tractive effort may be above the second threshold (for example, above 130 klbs). When located in operating area 703, the lift options available are hold, and lift-min.
The locomotive may be positioned in a fourth operating area 704 when the locomotive speed is below the second threshold (for example, below 3 mph) and the tractive effort is above the second threshold (for example above 130 klbs). When located in operating area 704, the lift options available are hold, and lift-start. The locomotive may be positioned in a fifth operating area 705 when the locomotive speed is above the first threshold but below a third threshold (for example, above 10 mph and below 13 mph). Furthermore, in this operating area, the tractive effort available is no more than 90% of the maximum tractive effort possible for the engine's given horsepower. When located in operating area 705, the lift options available are hold, lift-run, and lift-min.
The locomotive may be positioned in a sixth operating area 706 when the locomotive speed is above the third threshold but below a fourth threshold (for example, above 13 mph but below 17 mph) and the tractive effort is below 90% of the maximum tractive effort possible for the engine's given horsepower. When located in operating area 706, the lift options available are hold, lift-run, lift-min, and lift decrease (e.g., ramp down the lift amount). The locomotive may be positioned in a seventh operating area 707 when the locomotive speed is above the first threshold but below the fourth threshold (for example, above 10 mph but below 17 mph) and the tractive effort is above 90% of the maximum tractive effort possible for the engine's given horsepower. When located in operating area 707, the lift options available are hold, lift lift-min and lift-decrease. Finally, the locomotive may be positioned in an eighth operating area 708 when the locomotive speed is above the fourth threshold (for example, above 17 mph). When located in operating area 708, the lift options available are hold, and lift-decrease, where a determined amount of lift may be limited to lower amounts as the vehicle speed increases. As such, above a fifth threshold speed, such as critical speed (speedcrit), the locomotive may not be operated with lift anymore. In one example, the critical speed may be 18 mph. In alternate examples, the determined amount of lift may be limited to lower amounts as the vehicle speed increases, for example, as the vehicle speed increases beyond the threshold speed. By preempting a weight shift to the powered axles at speeds above a threshold speed, the compressed primary suspension mode may be avoided at higher speeds, thereby reducing the detrimental impact thereof on ride quality and track forces.
As mentioned, based on the locomotive operating conditions, and further based on the position of the locomotive in map 700, potential lift commands may be determined. In one example, when the locomotive is in operating area 701, and the locomotive notch is above a threshold, for example, notch 5, the pressure commanded to the lift mechanism actuators may be increased. In comparison, when the notch is below 5, the pressure commanded to the lifters may be held. In another example, when the locomotive is in operating area 702, and the locomotive is in a stalled state, or is starting with a lift, or when the truck chain tension is below a threshold, for example, the truck chain tension has not persisted at 4000 lbs for more than 1 second, the pressure commanded to the lift mechanism actuators may be increased. Else, the pressure commanded to the lifters may be held. In yet another example, when the locomotive is in operating area 703, and the truck chain tension has not persisted at 4000 lbs for more than 1 second, the pressure commanded to the lift mechanism actuators may be increased. Else, the pressure commanded to the lifters may be held. In still another example, when the locomotive is in operating area 704, and the locomotive is starting with a lift, the pressure commanded to the lift mechanism actuators may be increased. Else, the pressure commanded to the lifters may be held.
In another example, when the locomotive is in operating area 705, and the truck chain tension has not persisted at 4000 lbs for more than 1 second, the pressure commanded to the lift mechanism actuators may be increased. Else, the pressure commanded to the lifters may be held. In yet another example, when the locomotive is in operating area 706, and the truck chain tension is more than a threshold, for example, has persisted at more than 36000 lbs for more than 1 second, the pressure commanded to the lift mechanism actuators may be decreased.
In another example, when the locomotive is in operating area 707, and the truck chain tension has persisted beyond 6000 lbs for more than 1 second. Else, the pressure command may be held. In still another example, when the locomotive is in operating area 708, and the locomotive speed is above the critical speed, the same thresholds as described for area 707 apply for pressure reductions in area 708 except there is no requirement for a minimum chain tension.
Now turning to
Lift selection algorithm 802 may calculate lift command 820 based at least on the operating area 807 of the locomotive, e.g., the position of the locomotive in the lift condition map of
Lift command 820 may also be adjusted responsive to a braking condition, for example, as determined by a brake cylinder pressure 806. For example, in response to vehicle braking (e.g., when brake cylinder pressure is greater than a threshold), the determined amount of lift may be reduced. In one example, in response to vehicle braking, a de-lift operation may be commanded and the lift may be reduced to a condition of substantially no lift, for example by opening a dump valve of the lift mechanism.
The lift selection algorithm 802 may also receive input regarding vehicle slip 808, (for example, the presence or absence of slip, an amount of vehicle slip, the number and identity of slipping axles, etc.). The algorithm may additionally consider sanding interactions 810. The sanding interactions 810 may enable sanding control to be coordinated with the lift control to reduce the amount of dynamic weight redistribution. As such, the sanding operation may be applied to improve the tractive effort of the vehicle, for example, in response to a reduction in tractive effort due to wheel slip. For example, in response to a vehicle stall risk, for example due to wheel slip, the controller may first attempt to sand the rails. Then, in response to the effect of the sanding on the slip, an amount of lift may be adjusted. For example, if the sanding helps to improve the tractive effort, the lift mechanism may not necessitate activation. In another example, if the sanding does not help to reduce the slip and increase tractive effort, the lift operation may be increased. In one example, in the presence of vehicle slip and in response to a vehicle sanding operation, if vehicle slip has not substantially decreased, then the amount of lift commanded may be increased. In comparison, in the presence of vehicle slip and in response to a vehicle sanding operation, if vehicle slip has substantially decreased, then the amount of lift commanded may be decreased. Sanding interactions may also compensate for a weight of sand within a locomotive sand applicator. In still other examples, the lift mechanism may be commanded to perform a lift before the automatic sand application on order to reduce sand use. For example, when the amount of sand is above a threshold, a controller may attempt to improve the tractive effort with the sand application first, and then apply a lift command if the sand application does not produce the desired tractive effort. In contrast, when the amount of sand is below a threshold, for example, the controller may perform a lift command before the sand application.
Lift command 820 may also be adjusted responsive to a vehicle penalty 809. A vehicle control system may include computer readable storage medium with instructions for determining a vehicle penalty. The vehicle penalty may include a combined truck penalty for the multiple trucks, as well as penalty for the various other locomotive components. As such, the penalty may reflect the amount of stress on the various locomotive components and the underlying rail. The vehicle penalty may be determined based on at least lift mechanism component stress, wheel slip, vehicle stall risks, fuel level, and lift mechanism actuator forces. Based on the determined vehicle penalty, the control system may limit the determined amount of lift. The limiting may include, reducing the determined amount of lift as the determined vehicle penalty increases. In one example, in response to the vehicle penalty being below a threshold, the lift command may be increased. In another example, if the vehicle penalty is above the threshold, the lift command may be reduced and/or a de-lift operation may be commanded to reduce component over-stress and potential vehicle slide.
The lift command may also be adjusted based on infrastructure conditions 805. The infrastructure conditions may include, for example, one of a reduced track quality, a reduced bridge stability, a reduced ballast quality, and a reduced tie quality. In response to an infrastructure condition, the determined amount of lift may be reduced and/or limited. For example, the amount of lift may be limited to lower amounts when the quality of the rail track is poor. In one example, as previously elaborated, the infrastructure conditions 805 may be determined from a track database and/or a global positioning system (GPS). In another example, the infrastructure condition may be manually input. In another example, the amount of lift may depend on the strength or type of infrastructure over which the locomotive is operating (such as a bridge). A GPS along with on-board track database or other wireless communication, may determine infrastructure conditions 805 at any given time.
The lift command may, similarly, be adjusted based on the gradient of the track on which the locomotive is running, or will be running. In one example, the hill state or grade may be recalculated at the start of a vehicle operation. In another example, the grade or hill state may be determined from a previous vehicle shut-down (for example, by storing the details of the grade or hills state in a controller memory during the previous shut-down). In another example, the grade may be determined and/or adjusted based on input from a track database and/or a global positioning system included in the locomotive cab (for example, as part of an on-board control system). The lift may be adjusted based on the presence or absence of a hill condition (e.g., based on a gradient and/or a degree of the gradient), and further based on whether the gradient is present at the time the vehicle is starting to operate or later. For example, the lift may be adjusted when the vehicle is starting on a hill. This is because the weight distribution between the axles may be markedly distinct when starting the vehicle on a hill in comparison to starting the vehicle on a flatter ground. In one example, the amount of lift may be based on the grade of the vehicle during the initial movement of the vehicle from rest. For example, the determined amount of lift may be increased in response to an increase in grade. Similarly, the transitions between lift commands, (transitions among increasing lift, decreasing lift, and holding lift commands) may be adjusted based on the track grade. Further still, the lift command may be adjusted based on whether the locomotive is in a start condition, non-start condition, or restart condition.
In addition, the amount of lift may be further adjusted, for example, limited, in response to conditions external to the vehicle, including environmental and weather conditions, such as an ambient temperature, pressure, humidity, and weather. For example, in response to a weather condition, a controller may further limit the determined amount of lift. In one example, during higher ambient temperatures, the amount of lift may be limited to lower amounts to reduce heat stress on the wheels. In another example, then amount of lift may be further limited in the event of rain and/or snow to reduce vehicle slide. As such, when an amount of lift is to be increased or decreased, the controller may also determine a corresponding ramp-up rate or ramp-down rate, respectively. The ramp-up and/or ramp down rates may be based on parameters including, a level of lifting, a vehicle speed, and a tractive effort.
Now turning to
Following a powering up of the locomotive, the locomotive may initially be in the state of no_stall 902. From here, the locomotive may only be transitioned to a state of stall_setup 906 wherein it may be determined whether there is an imminent stall risk or not. The locomotive may enter stall_setup 906 from no_stall 902 in response to conditions 904 including, the locomotive notch being above a threshold value (sds_enter_notch), for example, above notch 8, the locomotive being in a motoring condition, and the locomotive speed being below a threshold speed (sds_setup_spd), for example, below 11 mph. Additionally, a controller may note the speed at which the locomotive enters the stall_setup state (stall_speed). The locomotive may return from stall_setup 906 to no_stall 902 in response to conditions 916 including, the locomotive notch being below a threshold value (sds_exit_notch), for example, below notch 5, the locomotive being in a non-motoring condition, or the locomotive speed being above a threshold speed (sds_setup_spd), for example, above 11 mph.
The locomotive may enter stall 910 from stall_setup 906 in response to conditions 908 including the locomotive speed falling below the stall speed (stall_speed) by a threshold amount (sds_delta_spd), for example, falling by 2 mph. As such, while waiting for the speed to drop, the locomotive may be maintained in stall_setup 906.
The locomotive may return to no_stall 902 from stall 910 in response to conditions 912 including, the locomotive notch being below a threshold value (sds_exit_notch), for example, below notch 5, the locomotive being in a non-motoring condition, or the locomotive speed being above a threshold speed (sds_cutoff_spd), for example, above 17 mph. In this way, during conditions of low speed and high notch, when the locomotive is motoring, a controller may predict a vehicle stall and adjust the lift operation accordingly.
It will be appreciated that a variety of lift commands may be possible, based on the vehicle operating conditions, to thereby adjust a vehicle lift mechanism. In one example, the adjustment may include, during a first operating condition, increasing a determined amount of lift, maintaining the determined amount of lift during a second operating condition, and decreasing the determined amount of lift during a third operating condition. In a second example, the adjustment may include, during a first vehicle operational range, maintaining the determined amount of lift in response to increased wheel slippage, and during a second vehicle operational range, increasing the determined amount of lift in response to increased wheel slippage. In this way, lift commands may be dynamically adjusted responsive to vehicle operating conditions. By adjusting the lift commands dynamically, the lift mechanism of the vehicle may be adjusted to thereby enable the dynamic weight redistribution. By performing adjustments to the lift operation to compensate for vehicle slip, sanding interactions, truck conditions, track gradients, etc., potential locomotive damage may be substantially reduced.
This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
