Abstract:
An interface system is presented, which prevents operational interference between a vehicle power door and a ramp of an access system by interrupting power to the motors and actuators responsible for operating the door. The interface system includes a relay system that does not interrupt, read, signal, or otherwise interfere with the communication lines between a body control unit, door control unit, or remote control transmitter or receiver. Thus, the interface system functions without the need to receive and transmit signals on the vehicle&#39;s communication bus. The interface system enables the ramp controller of the access system to be a separate module, which controls the ramp and kneel functions, because the only input the ramp controller provides to the power door system is to a ground signal that mimics that of a switch included in the vehicle.

Description:
BACKGROUND 
   Access systems, such as motorized lifts, have been used to transport people and cargo. These access systems include platforms, ramps, moving seats, movable steps, and the like, which may be attached to stationary structures, such as buildings and loading docks, or mobile structures such as vehicles. Access systems have been used to provide disabled individuals access to structures that traditionally were accessible only via steps or stairs, or required an individual to step over or across an obstacle. For example, motorized lifts have been used to allow disabled individuals to enter and exit vehicles. In another example, motorized lifts have been used to load and/or unload stretchers from vehicles, such as ambulances. Motorized lifts have also been used on loading docks and trucks to allow cargo to be loaded, unloaded or otherwise moved. 
   When an access system is installed in a vehicle, it is generally integrated with the power sliding door system of the vehicle. The power sliding door system opens or closes the door when it receives a request to do so (a “door operation request”). The power sliding door system further includes a body control unit, door control unit, receiver, door switch and data bus. The body control unit, door control unit, receiver and door switch are all in communication with the vehicle&#39;s data bus, which enables body control unit, door control unit, receiver and door switch to communicate with each other and to receive a signal from a user indicating that the user wants to open or close the door (a “door operation request”). Generally, the user may communicate a door operation request to the power system door system by pulling on a door handle of the vehicle or pushing a button on a keyless entry device. If the door operation request is produced by a remote device, the power sliding door system receives the door operation request via the receiver. If the door operation request is produced by movement of the door handle, the door operation request causes the door switch to close, which communicates the door operation request to the power sliding door system. 
   When a door operation request received by the power sliding door system, it is initially received by the body control unit. The body control unit evaluates whether it is an appropriate time to operate the door. For example, the body control unit may receive signals via the data bus indicating the status of the transmission position, speed and door lock position of the vehicle. If the body control unit determines that the status of the vehicle are acceptable, the body control unit communicates a command to operate the door (a “door operation command”) to the motors and switches that unlatch the door and either open or close the door. 
   Access systems are installed in vehicles with a power sliding door system as described above, so that the operation of the ramp by the access system and operation of the door by the power sliding door system do not interfere with each other. To prevent such interference, the access system may be installed so that it receives the door operation commands from the body control unit. The access system will only communicate the door operation command when it determines that the ramp is fully stowed. This method requires the access system to be in communication with the data bus of the power sliding door system, either directly or through a gateway. However, vehicle manufacturers are becoming less willing to allow access systems to communicate with the data bus and thus, unwilling to allow access systems to be installed and operate in the manner described above. 
   SUMMARY 
   An interface system is presented, which prevents operational interference between a vehicle power door and a ramp of an access system by interrupting power to the motors and actuators responsible for operating the door. The interface system includes a relay system that does not interrupt, read, signal, or otherwise interfere with the communication lines between a body control unit, door control unit, or remote control transmitter or receiver. Thus, the interface system functions without the need to receive and transmit signals on the vehicle&#39;s communication bus. The interface system enables the ramp controller of the access system to be a separate module, which controls the ramp and kneel functions, because the only input the ramp controller provides to the power door system is to a ground signal that mimics that of a switch included in the vehicle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, the same reference symbols designate the same parts, components, modules or steps, unless and to the extent indicated otherwise. 
       FIG. 1  is a block diagram of a switch-based interface system as implemented between a power sliding door system and a ramp controller; and 
       FIG. 2  is a circuit diagram of a switch-based interface system. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a switch-based door and ramp interface system (an “interface system”)  100  as implemented in a vehicle so as to prevent operational interference between a ramp of an access system (controlled by a control system  106 ) and the door of the vehicle (controlled by a door control unit  104 ). The door control unit  104  opens and closes the door of the vehicle upon receiving a request from a user to do so, and is generally installed in the vehicle by the manufacturer of the vehicle. The ramp control system  106  and the remainder of the access system (not shown) deploys and stows a ramp to provide an alternative path for entering and exiting the vehicle. Unlike the door control unit  104 , ramp control system  106  and the remainder of the access system (not shown) is generally installed by a third party after the vehicle has been manufactured. Therefore, it is unlikely that the door control unit includes a mechanism that will prevent operational interference between the door and the ramp. As a result, the interface system  100  is generally installed in the vehicle with the access system. 
   The interface system  100  prevents operational interference between the ramp and the door by interrupting power communicated by the door control unit  104  to the controllers that operate the motors and switches responsible for opening and closing the door when the ramp is not fully stowed. The interface system  100  does not communicate with the data bus  140  nor does it receive any control signals from the body control unit  104 . As shown in  FIG. 2 , the interface system  100  includes a group of relays  230 ,  232 ,  234 ,  236 ,  244  and  248  that control operation of the door. Alternately, the interference system  100  may include transistors. As shown in  FIG. 1 , the interface system  100  is implemented between the door control unit  104  and the latch release actuator  108 , and between the door control unit  104  and the motor and clutch controller  132 , which actually moves the door. The latch release actuator  108  unlatches the door from the frame of the vehicle so that the door is free to move. The motor and clutch controller  132  then moves the door. Therefore, by interrupting the power to the latch release actuator  108  and the motor and clutch controller  132 , interface system  100  prevents operation of the door. 
   The interface system  100  interrupts the power to the latch release actuator  108  and the motor and clutch controller  132  when a door operation request is received by the door control unit  104  and the ramp is not fully stowed. As shown in  FIG. 2 , the interface system  100  includes a door relay  232  and a motor and clutch relay  234 . The door relay  232  is coupled between the door control unit  104  and the latch release actuator  108 . The motor and clutch relay  234  is coupled between the door control unit  104  and the motor and clutch controller  132 . The switch  268  of the door relay  232  remains open until the coil  264  is activate. Therefore, when the door control unit  104  communicates a power signal, the power signal will be interrupted by the door relay  232 . Similarly, the switch  272  of the motor and clutch relay  234  remains open until the coil  270  is activated. The coils  264  and  270  are activated when the ramp is stowed. When the ramp is no longer fully stowed, the ramp stowed switch  114  will open, causing the coils  264  and  270  to deactivate and the switches  268  and  272 , respectively, to open. Thus, the power to the latch release actuator  108  and motor and clutch controller  132  are interrupted. 
   The interface system  100  controls the power to the latch release actuator  108  and motor and clutch controller  132  as described above when the door operation request is communicated with the door control unit  104  by the body control unit  102  ( FIG. 1 ). Although the door control unit  104  contains software and hardware that controls the proper operation of the door latches and motors, the door control unit  104  needs to receive authorization from the body control unit  102  before communicating a door operation command. The door control unit  104  authorizes the door control unit  104  by communicating door operation requests to the body control unit  102  when certain conditions are met. For example, the body operation function may monitor several switches mounted at various places inside the vehicle, which reflect conditions such as transmission position, vehicle speed, and door lock condition. These switches are tied to chassis ground and when depressed send a ground (low) signal to the body control unit  102 . If the body control unit  102  determines that the conditions are met, it then sends a door operation request to the door control unit  104 . 
   The body control unit  102  may receive a door operation request from a sliding door satellite switch  101 . Alternately or additionally, the body control unit  102  may receive a door operation request from a remote transmitter  122  via a remote receiver  120  (which may be located inside the vehicle) and a data bus. The remote transmitter  122  may enable keyless entry into the vehicle by communicating a door operation request to the body control unit  102 . The remote transmitter  122  may include a button, be mounted on a keychain and may issue a door operation request when the button is pushed. 
   However, if the door operation request is communicated with the door control unit  104  without going through the body control unit  102  first, the interface system  100  may control the power from the door control unit  102  in a different manner. Such door operation requests may originate from a pillar switch (such as B pillar switch  220 , C pillar switch  222 ) an optional switch  224 , the vehicle&#39;s inside door handle  110  or the vehicle&#39;s outside vehicle door handle  112 . As shown in  FIG. 1 , when a pillar switch  220 ,  222 , optional switch  224  or door handle switch  110 ,  112  is activated, it sends a ground (low) signal to the door control unit  104 , bypassing the body control unit  102 . 
   For the sake of example only, the following will discuss operation of the interface system  100  when the outside door handle switch  112  is activated. The discussion that follows applies when the inside door handle switch  110 , pillar switch  220 ,  222  or optional switch  224  is activated. 
   When the outside door handle is activated by, for example, a user entering the vehicle who does not wish to use the ramp, the outside door handle switch  112  is closed, thus communicating a door operate command to the door control unit  104 . However, under these conditions, the ramp interface system  100  may prevent the ramp from deploying and the vehicle from kneeling to prevent the ramp from hitting the user on the head. To allow the door to open and prevent the ramp from deploying, the interface system includes a door handle detection relay  248  and a ramp signal relay  236  that recognize this situation and control the ramp and kneeling under this situation. In general, if the door handle detection relay  248  and the ramp signal relay  236  detect that a door control request has been sent to the door control unit  104 , the two relays  248  and  236  send signals to the ramp controller  106  indicating that the ramp and kneel are already deployed and lowered, respectively. Because the ramp controller  106  detects that the ramp is deployed and the vehicle kneeled, the ramp controller  106  will not deploy the ramp. 
   Upon receiving the door operation command from the outside door handle switch  112 , the door control unit  104  may send power to the latch release actuator  108  and to a trigger relay  106 , thus activating the trigger relay  106 . The activated trigger relay  106  communicates a ground signal to the ramp controller  206 , which activates the ramp controller  106 . If the ramp is deployed, the ground signal causes the ramp to stow. When the ramp is fully stowed, the ramp stowed switch  114  closes, which communicates a ground signal to the door control unit  104  to repeat the process in order to close the door. If the ramp is stowed when the door control unit  104  sends power to the motor and clutch controller  132 , the door closes. 
   If the door is closed when the outside door handle  112  is operated, the door will start to open. The ramp controller  106  includes a sensor that communicates a signal to the ramp controller  106  when the door is active, which prompts the ramp controller  106  to activate as well. However, the door handle detection relay  248  is also activated which sends a ground signal to the ramp signal relay  236 . The ramp signal relay  236  communicates a ground signal to the ramp deployed input  134  and the kneel lowered input  136  of the ramp controller  106  so that the ramp controller senses that the ramp is deployed and the vehicle is lowered (kneeled), even though they are not. Thus, when the door is fully open, the ramp controller  106  will not deploy the ramp. 
   The door close output  113  of the ramp controller  106  is communicated to activate the ECU trigger  244 . The ECU trigger  244 , when activated, sends a ground (low) signal that duplicates the B pillar switch. This ground signal is transmitted to the OEM door control unit  104  which interprets this signal as a request to operate the power slide door from the B Pillar switch  220 . The ramp controller  106  only communicates out this ground signal once it senses that the ramp is fully stowed. Because the ramp is fully stowed, the door relay  232  and the motor and clutch relay  234  are closed, thus, a new request from any switch will cause the door to close. 
   While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.