Crop Shear Control System

This project CROP SHEAR CONTROL SYSTEM  involved the design and development of a shear control system for M/s. Tata Iron and Steel Company, Jamshedpur.

Important Events:

  • The prototype of the system was tested successfully using a DC motor.
  • Published a paper on “ Design development and implementation of Crop Shear Control System using Digital Signal Processor”, 4th International Seminar on Power Electronics and Automation, INTRONICS-99, IEEMA, January, 1999.

Brief Description :

  • The crop shear control system is developed for cutting the head and tail ends of a moving hot metal strip to proper shape, required in steel industries. The shear position is controlled optimally with respect to the moving sheet, to achieve the required accuracy. Most effective control is provided by cascading torque, acceleration, speed and position loops along with feedforward control.
  • The control system is implemented using the Digital Signal Processor TMS320. The DSP based control unit is connected to a PC through an RS232 communication link. A convenient user interface is provided in the PC for configuring the system and changing parameters . The various algorithms for the operation of the controller are written in ‘C’ and cross-compiled with TMS320 ‘C’ compiler. Broadly the programs are divided into measurement routines, off line routines and online routines. Measurement algorithms are processed as timer interrupt routines. Off line and online programs involve the calculation of feedforward reference trajectories for acceleration, speed and position of shear. Some of the computations that can be done before starting the cut are put in off line routine to save computation time during the online process.
  • External interrupt routines are used for initializing the measurements and starting the online calculations. The online programs also calculate the Proportional Integral and Derivative control (PID) law from the predicted error for position control. The algorithms resident in the DSP also check all the preconditions to be met for the satisfactory operation of the shear drive system and thereof positioning of the shear knives to the defined waiting position, if it is already not in waiting position.
  • A user-friendly graphical interface is designed to enter the required tuning parameters of the system and establish a two-way communication between PC and DSP system. After entering the required parameters, the user can initiate the process of cutting, by sending these values and handing over the control to DSP system. Once the control is passed to DSP system, the PC get itself switched over to monitoring mode. Now, the status of initialization of the knives, their movements etc., will be communicated to PC and are displayed on the monitor, in the space provided for this purpose. If there is any problem encountered with those operations (e.g. a switch has to be turned off), the same is displayed on the screen, with continuous beep sounds, so that the operator can rectify them. After the cutting process is over, the data required to plot the trends are passed from DSP to PC and are stored in appropriate log files.

Hardware Specifications

Mother Board

Processor TMS320C32 Floating Point DSP
External Bus 32-Bit
Memory EPROM – 64K to 256K RAM
Serial Ports 1 RS232 & 1 RS485
32-bit Timers 2
Supply Voltage +5V
Status Display 5 LEDs
Back plane Bus VME Compatible (6 expansion slots)
Board Size Double Euro (160 * 233.3 mm)

Process Interface

Digital Inputs 9; High Speed Opto-Isolated
Digital Outputs 2; Relay Contacts
Analog Inputs 2; 12-bit res. 2000V DC Isolation
Analog Outputs 3; 12-bit res. 2000V DC Isolation
External Interrupts 3; High Speed Opto-Isolated
Incremental Encoder Inputs 2; Quadrature Decoder Inputs
Absolute Encoder Inputs 1; 16-bit Gray-code Input