Abstract:
A method of operating an automated guided cart may include directing, using a controller, the cart on a production operation path; automatically detecting a state-of-charge in an on-board battery pack; signaling to a remote station the state-of-charge; and when the state-of-charge is below a predetermined charge limit, the remote station automatically signaling the cart to automatically veer from the production operation path to a low battery charge path and stop at a battery station.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to automated guided cart systems, and more particularly to control of such systems. 
     Automated guided carts may be employed in factories to move items from one location to another. These carts operate autonomously without a human operator driving the cart. Such carts may use batteries to power an electric motor to propel the cart. However, in such operating conditions, there may be times when the batteries of a particular cart are discharged during use, thus stranding the cart. This may result in lost production at the factory. Some attempts at solutions to this concern, for example buying more expensive equipment/batteries or employing automatic charging pads, may be more expensive than desired. 
     SUMMARY OF INVENTION 
     An embodiment contemplates a method of operating an automated guided cart that includes: directing, using a controller, the cart on a production operation path; automatically detecting a state-of-charge in an on-board battery pack; signaling to a remote station the state-of-charge; and when the state-of-charge is below a predetermined charge limit, the remote station automatically signaling the cart to automatically veer from the production operation path to a low battery charge path and stop at a battery station. 
     An embodiment contemplates an automated guide cart system including: an automated guided cart including an on-board battery pack, an on-board controller that directs the cart on a production operation path and automatically detects a state-of-charge in the on-board battery pack, and an on-board transceiver to transmit a signal relating to a state-of-charge of the on-board battery pack; a stationary remote station having a stationary transceiver to communicate with the on-board transceiver, and a controller to direct the cart, via a signal from the stationary transceiver, to continue on the production operation path or to steer onto a low battery charge path when the state-of-charge of the battery is below a predetermined threshold. 
     An advantage of an embodiment is that automated guide carts, during normal operation, may be automatically routed offline for battery replacement when low battery charge is detected. This may help reduce or eliminate downtime of such carts due to discharged batteries. Also, the cart is moved to a location that allows for quick battery replacement. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic of an automated guided cart system and control in a factory. 
         FIG. 2  is a schematic figure of a remote station employed with an automated guided cart system. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an automated guide cart system  8  includes an automated guided cart  10  that is shown on a factory floor  12 . The cart  10  may include a battery pack  14  that powers an electric motor  16 , which drives wheels  18 , and an automated steering assembly  20  that steers another set of wheels  22 . The cart  10  may also include a controller  24  that is in communication with the steering assembly  20 , battery pack  14  and motor  16 . The controller  24  may be in communication with a battery charge detector  25 , which can detect the state-of-charge of the battery pack  14 . The detector  25  may any one of a number of devices that can detect the state-of-charge of a battery, as are known to those skilled in the art. The cart  10  may also include an on-board transceiver  26  for communication between the controller  24  and a remote station  28  mounted at a location on the floor  12 . 
     The remote station  28  may include a power supply  30 , which may be the electrical power supply in the factory, and a controller  32 , which is in communication with a transceiver  34  that communicates with the on-board transceiver  26 . The transceivers  26 ,  34  may communicate with each other, by transmitting data by, for example, infrared or radio transmission, as the two transceivers  26 ,  34  pass close to one another along a guide path  36  that the cart  10  follows. 
     The guide path  36  may be, for example, a magnetic tape that is secured to the floor  12 . The guide path  36  is the path along which the cart  10  travels while conducting production operations to deliver parts (or other activities) around the factory floor  12 . At a location on the floor  12 , the guide path  36  may fork into continuing on a production operation path  38 , where the cart  10  continues on the path to deliver parts, assemblies, etc. associated with regular duties in the plant, or a low battery charge path  40 , which directs the cart  10  to a battery station  42 . 
     The battery station  42  may include one or more spare battery packs  44 , and may include a battery charger  46 . If this location includes the battery charger  46 , it may be used to charge the spare battery packs  44  and/or the battery pack  14  on the vehicle, as the particular situation may warrant. The battery station  42  may also include some type of battery change indicator  48  that can be used to notify a factory worker that the cart  10  is at the station  42  and needs a battery change or recharge. 
       FIG. 2  illustrates an example of how the remote station  28  may be configured. The power supply  30  may include a neutral line  52  and a one hundred twenty volt supply line  54 , with a circuit breaker  56 , the supply line supplying power to a power supply converter  58 . The power supply converter  58  may convert the power to, for example, twenty four volts, with a power line  60  and a common line  62 . The controller  32  may have various inputs—for example, there may be a power input  64  and an input  66  from the transceiver  34 . The controller  32  may also have outputs  68 . One output  70  may be a normal condition output that outputs a high signal when the battery condition is sufficiently charged. Another output  72  may be a battery low condition output that outputs a high signal when a low battery charge is reported. 
     The operation of the automated guide cart system  8  will now be described with reference to  FIGS. 1 and 2 . As the cart  10  travels around the factory floor  12  along the guide path  36 , moving parts or performing other automated operations, the on-board controller  24  monitors the state-of-charge of the on-board battery pack  14 . As the cart  10  passes the transceiver  34  of the remote station  28 , if the battery pack charge is low, the on-board transceiver  26  will signal the low charge state, via the stationary transceiver  34 , to the remote station  28 . The output of the controller  32  will signal, via transceiver  34 , for the controller  24  to either continue to steer the cart  10  along the production operation path  38 , if the battery charge is adequate, or steer the cart  10  onto the low battery charge path  40 , if the charge of the on-board battery pack  14  is low. This, in effect, acts similar to an automated railroad switch to switch along which path the cart  10  will travel, without needed any human intervention. On the low battery charge path  40 , the cart  10  will then pull alongside the battery station  42  for replacement of the battery pack  14  with a charged spare battery pack  44 . The battery charge indicator  48 , if there is one, may be activated in order to alert a factory worker that a battery change is needed. Or, the battery station  42  may be located on the factory floor  12  close to a work station so that a worker close by will naturally notice when a cart  10  pulls into the station due to a low battery charge. The battery pack  14  may then be swapped out for the spare battery pack  44 , and the cart  10  activated to return to the production operation path  38  to continue with its operations on the factory floor  12 . 
     How low the battery pack charge is before the cart  10  is directed to the battery station depends upon the particular situation in which the cart is used and the battery packs being used. Thus, a predetermined charge limit threshold for low battery charge can be empirically determined. 
     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.