Revision as of 15:57, 3 December 2014

Lift Project is one of the projects designed in department of computer engineering at TTU as a lab project. The process of this lab is described in Fig. 1.

Fig. 1: Schematic of physical model

Physical Model

Lego Construction

A lego model has been built for this lab. you can see the schematic of the model in Fig. 2.

Fig. 2: Schematic of physical model

Fig. 3: Stepper motor setup in lego model

Controller circuit

first prototype

In the first verion of control board, a XULA fpga board has been used. Pin configuration of this board has been shown in Fig. 4.

Fig. 4: Schematic of control board

The following code is the UCF file for XULA board:

NET "clk" LOC = P43;
NET "m0" LOC = P56; # Direction 
NET "m1" LOC = P13; # step clock
NET sleep LOC = P44; # sleep to disable the motor

NET "ss(6)" LOC = P37;
NET "ss(5)" LOC = P36;
NET "ss(4)" LOC = P57;
NET "ss(3)" LOC = P61;
NET "ss(2)" LOC = P62;
NET "ss(1)" LOC = P50;
NET "ss(0)" LOC = P52;

NET "calls(0)" LOC = P21; 
NET "calls(1)" LOC = P32;
NET "calls(2)" LOC = P33;
NET "calls(3)" LOC = P34;
NET "calls(4)" LOC = P35;

NET "menu(0)" LOC = P3;
NET "menu(1)" LOC = P4;
NET "menu(2)" LOC = P7;
NET "menu(3)" LOC = P19;
NET "menu(4)" LOC = P20;

NET "sensors_in(0)" LOC = P39;
NET "sensors_in(1)" LOC = P68;
NET "sensors_in(2)" LOC = P82;
NET "sensors_in(3)" LOC = P97;
NET "sensors_in(4)" LOC = P94;

The first prototype control board provides the following functionalities:

• Seven segment display
• Inner and outer cabin push buttons
• Motor state indicator LEDs
• software reset button

Signal Names and Description

The first prototype board has the following signals:

Description

• Sensors should be designed according to the following functionality (see Fig. 5):

Fig. 5: Sensor setup on the lego structure

• • Sensors are prone to bouncing because of vibrations in the lift which might not be visible to the naked eye but is visible to the sensors. Hence the sensors need to be de-bounced by a three bit shift register with 19th bit of counter slowing the de-bouncing circuit.
  • The lift has five ray cut Infra-Red (IR) sensors.
  • When ever a sensors ray is cut by the lift it sends a signal '1' to the FPGA. Otherwise the sensor sends a '0'
  • Each sensor is placed between floors and there can be blind spots between each sensor. When the lift is in a blind spot all sensors send "00000" to the FPGA. This is the time when the lift is moving between two sensors. At this point sensors can also recieve value from two sensors as well. (e.g. on the second floor sensors can either have a value "00000" or "00110".) It is recommended that both cases should be handled by the designer. (hint: rather then looking for sensor ="00100" look for sensor(2)= "1".)
• Motor Signals
  • Motor(0) controls the direction of the motor. Where '1' is DOWN '0' is up
  • Motor(1) generates a clock signal which controls the speed of the motor. The speed is specified by a clk like signal by changing its frequency. The recommended speed of Motor can be given by sending 10th bit of the counter.
  • A sleep signal turns off the motor. In idle state the motor should be kept turned off. where '1' is ON and '0' is OFF
  • Motor FSM should also shares its Status with Floor FSM ( i.e. idle, going up, going down, blinking Seven segment)
• Seven segment should work as follows
  • Seven segment decoder decodes the current floor into seven segment output.
  • Each segment is turned on by logic value 1. Seven segment should also be able to blink 5 times after it reaches a floor.
  • Seven segment the pin orientation (i-e. seven segment <= "abcdefg";)

Safty Monitoring System

Since this model is designed to be controled remotely, it should be able to maintain its functionality even if it is programmed with a faulty design. For this reason we need some monitoring system to guarantee the functionality.

hardware break

A physical switch has been installed on the top floor to prevent faulty designs to go through the roof.

behaviour monitor

Since reaching hardware break will require human intervention and it would not always possible (in times that an operator is not present etc.), a behavior monitor system has been added to the lift. Motor control signals goes through the monitoring system and if it detects a suspicious behaviour (being on first floor and unwinding the thread or being on the top floor and trying to move up) it takes over the control and brings the lift to the initial position and sends a reset signal to the control board.

Lab Reports

A lab report template has been provided for students. You can find it here: File:lab6_template.pdf

Testing

Simuation

A VHDL testbench has been designed to be used for verifying the functionality of the lift.

Remote Lab

in this project, a remote lab was designed for students to access the controlling hardware from any remote place inside the department INTERA network. The server is running on a raspberry pi and students can see a view of the working lift using an internet camera. A working sample of the controller is provided to the students as a demo in order to get them accustomed to the functionality of the Lift. you can access this lab from this link: cherry.pld.ttu.ee

Web Server

• server on Raspberry Pi
• username and password for restrictions on access
• internet webcam

Push button emulator

• using Raspberry Pi GPIO for emulating push button behaviour

Future Work

• queueing system for login in remote lab
• checking the bitfile for malicious code
• making a 3D model for printing
• providing access for students outside ATI interanet
• PCB design for control board
• adding a micro-controller based control board
• monitoring all the sensors in monitoring system