TGPG Theory

The Ethernet Controller chip controls the 10Base-T connection with the console.

The TGPG has three CAN channels, and CAN1 is used for Gantry cover Push Buttons and Displays. CAN3 is used for connection to the Global table. CAN2 is used for the axial servo motor.

LSCOM is the communication way between TGP and ORP via slip rings. It uses three signals: SER_SREF (reference signal), SER_OUTBOUND (transmit signal), and SER_INBOUND (receive signal). The LSCOM interface needs an isolated +/- 5Vdc bipolar power supply to power the driver/receiver circuits. In addition, optical isolation is maintained between the slip rings and the ORP logic circuits.

The TGP board outputs EXP_ENBL signal to the ORP board via a slip ring for interrupting EXPCMD signal to JEDI.

The table drive is commanded by the firmware via CAN network. A filtered 12V power and ground bus on the TGPG are necessary for the Table CAN communication. The Table CAN is optically isolated from rest of the TGPG and uses the 12V filtered power for the output stages of the opto isolators. The following signals are used between the TGPG and table:

• Asynchronous Table Cradle Sync Signal

  This signal is for communication from the TCB to the TGPG quickly with a differential signal that is received on the TGPG which creates a maskable interrupt to the TGPG processor.

• Asynchronous Gantry to Table Sync Signal

  The TGPG Table Sync signal is provided to allow the TGPG to send a signal to the Table quickly and asynchronously. The control of this output is available via registers on the TGPG.

• Table Speaker Differential Signal

  This is the differential signal that will provide the speaker signal to the table.

• Table Status Signal

  This is a differential signal generated by the TCB that indicates that the Motion Enable command from host is transmitting, watchdog is working correctly, and if firmware is satisfied.

• Table Drive Enable Differential Signals

  This is a differential signal that is sent to the TCB from the TGPG, which is used to provide for an electrical hard line from the Gantry Control Push Buttons, Remote Tilt Buttons, Smartview footswitches, and Service Tilt switches. This differential signal must be met in order for motion to be available in the table.

• Motion Enable Command Differential Signals

  This is a differential signal that is used to indicate to the TCB that E-Stop has been pressed and within 1.5 seconds, the 120VAC to the table will be turned off. This provides the TCB enough time to stop the cradle and prepare for the loss of power.

• Table Foot Switches

  The table foot switches are used to raise and lower the table remotely from the console. There are two foot switches on either side of the table. One for raising the table and one for lowering the table. The switches have an inverse logic dual path input. A read back and maskable change of state interrupt of each signal is available on the processor via FPGA. When the up pedal is active the up signal will be high into the processor. When the down pedal is active the down signal will be high into the processor.

Special connector is design for the KTCB interface, which is located at top side of TGPG. The table drive is commanded by the firmware via RS422.

• Cradle encoder feedback

  Table provides cradle encoder feedback to TGPG. TGPG decode Phase A and Phase B signal to calculate cradle current position.

• Table motion enable signal

  When table up/down movement, TGPG sends out one signal to enable motion. This signal is controlled by both hardware and firmware. This is used to indicate the KTCB that elevation motion is enabled and when it needs to stop movement, this signal will extend 1.5 seconds. The 120VAC to the table will be turned off when this signal inactive. 1.5 seconds provide KTCB enough time to stop the cradle and prepare for the loss of power.

• Kunlun table ID

  This is TTL signal, which is used to identify KTCB connecting to TGPG. If this signal is inactive, even if other signals normal, TGPG couldn’t work correctly to support KTCB.

• Cradle motion drive signal

  Cradle in/out movement is driven by TGPG pulse directly. The in/out pulse is sent to KTCB and then processed to control motor movement. In or out movement are controlled by 2 signals separately. If one signal was broken, it means one direction movement couldn’t be implemented.

• Latch and excitation

  There are two latch button connected to KTCB and KTCB transfer the signals to TGPG. Either of them is pressed, TGPG would consider cradle to need excitation off. And accordingly, excitation signal become inactive. In this condition, cradle can be pulled or pushed easily by hand.

• Table foot switch and Table Speaker Differential Signal

  It is the same as GTCB interface

This is a steady-state +24Vdc input signal from the Gantry to close the "X-Ray ON" Light relay. The x-ray interlock is passed through a relay on the TGPG. To close the relay, the watchdog circuit must be active and the relay must be commanded to close via TGP processor. The TGPG board will provide a set of 24v/40mA contacts to control a 24v relay in the PDU. The 24v PDU relay will close a set of 110VAC contacts that drive the hospital X-ray On Light. The 24v relay contacts will be closed (x-ray light turned on) whenever the TGPG board commands x-rays to the ORP. A register written to by firmware will command the x-ray on light’s relay. The bits of the register will be cleared in the event of a power failure, CPU fault, or watchdog / board fault condition.

Steady-state +24Vdc input signal from the Gantry to close the "System ON" Light relay. NGPDU provides isolated terminals for customer Room Light connections.

Steady-state +24Vdc input signal from the Gantry to close the "Generator Ready" Light relay. NGPDU provides isolated terminals for customer Room Light connections.

Two signals are provided for use with defined cardiac features: Exposure Command and R-Pulse. Exposure command is the same signal as the command of the same name described in the Scan Control section of this document, however it is also provided to the TGPG as a 422 signal for transmission to the board providing isolation for the EKG machine. R-Pulse is a signal, received from the Gantry Options board providing isolation for the EKG machine, which indicates that the heart is in a particular part of the cardiac cycle. The status of the R-Pulse signal and a mask able positive edge sensitive interrupt can be read back by the TGP via registers on the TGPG.

Two signals are provided for use with defined pulmonary features: Resp_mon and Resp-Pulse. Resp-Pulse is a signal, received from the Gantry Option board providing isolation for the pulmonary monitor, which indicates that the lungs are in a particular part of the volumetric capacity. The status of the Resp-Pulse signal and a mask able positive edge sensitive interrupt can be read back by the TGP via registers on the TGPG.

Smartview Footswitch : A footswitch is used by the operator to control scanning during a Smartview procedure. The footswitch consists of two switches, one normally open, and one normally closed, which each change state when the footswitch is pressed.

Smartview Hand Held Control: A hand held control is used by the operator to control scanning and table motion during a Smartview procedure. The hand held control consists of a RX/TX signal is controlled by the TGPG.

Signals from the axial encoder and azimuth detection board measure the gantry position. The gantry position is used to monitor axial drive positioning, velocity performance and to determine starting x-ray and view angles

Gantry Position is measured with an incremental encoder mounted on the gantry's motor drive shaft. The motor and encoder turn 13 times for every one gantry revolution. The encoder has two channels, A and B, in quadrature with a resolution of 2,048 pulses per channel per encoder revolution. There are (2,048 X 13) = 26,624 Ch. A and Ch. B encoder pulses per gantry revolution. Channel A and B taken in quadrature provide a 106,496 pulse per gantry revolution resolution. Encoder accuracy of 0.0135 degrees per channel pulse, or 0.00338 degrees per quadrature pulse. The TGPG provides a filtered +5v and ground to the axial drive motor encoder. This power is filtered to prevent tube spit noise from propagating in through the encoder cable and corrupting the TGPG.

The home position is the gantry position with the x-ray tube positioned at 12 o'clock. This position is sensed using an optical home flag and home flag sensor board. The home flag is a 1 inch wide piece of metal attached to the rotating bearing. The TGPG board supplies +5v to the home flag board. The home flag is used on the TGPG board in conjunction with the axial encoder “C” pulse to determine gantry home position for firmware.

If TGPG was connected to a new axial interface, gantry encoder interface may be ignored and the encoder feedback comes from the interface, which is generated by motor encoder. From this interface, TGPG can get the correct phase A and phase B encoder signals but phase C signal is not the same as gantry encoder. In this condition, gantry home position was calculated a little different from conventional axial interface. When TGPG get the rising edge of home flag, it would calculate the point and get the home position.

There is one identification signal from the new axial driver interface to note TGPG new interface is used. Once TGPG detect this signal during it booting up, it wouldn’t ignore the conventional interface.

The status of the axial drive enable switch can be read back by the TGPG. While the axial drive switch is in the disabled position, the axial drive enable output is forced inactive and the axial holding brake output is forced to release the brake. This signals are active both at conventional and new interface. This signal function is same both in conventional and new axial driver interface.

The axial holding brake, which is normally applied, is released by applying 120VAC to the brake leads. The 120 VAC is controlled by a solid state relay that in turn is controlled by the TGPG. Note that the TGPG axial brake output is forced to release the brake when the axial drive enable switch is in the disabled position. The axial brake is meant as a static brake to hold the gantry still once it has been positioned by the axial drive. The brake's friction is not sufficient to hold the gantry still against the full accelerating force of the motor and amplifier. Should the brake fail while the gantry is in motion, the gantry will continue to rotate until halted by firmware. The brake is also not sufficient to hold the gantry while the tube or inverters are being changed. Whenever servicing the rotating base, the gantry should be locked out using the locking pin mechanism. The axial brake is released when the Gantry Loop Contactor Service Switch is in the "disable" position. This allows the gantry to be rotated by hand without fighting the friction of the brake. This signal function is same both at conventional and new axial interface.

The axial motor drive is powered by two sources: The main source of power is from three phase 480VAC controlled by the axial power contactor. The second source of power is provided via the drive’s DC bus by the axial dynamic brake. The axial power control relay, axial drive enable switch and drives power must all be active for the axial power contactor to close.

The 480VAC axial power contactor can be read back when a maskable change of state interrupt occurs on the TGPG processor.

For the conventional axial driver interface, the axial drive is commanded by the firmware via CAN network. There are seven signals that are used on the CAN network: three control signals (Start, Stop and Enable) and four feedback signals (Fault, At Speed, At Freq. and At Pos.). An isolated power and ground bus on the TGPG is powered by a 12V supply from the axial drive. The axial CAN and control signals to the axial drive are optically isolated from rest of the TGPG and use the +5V isolated power for the output stages of the optoisolators. A detection circuit with read back via TGP processor is provided to determine if the isolated 12V power is being supplied to the TGPG. An 82527 CAN controller interface IC is used to provide CAN communications to the axial drive. The interrupt signal, “AX_DR_COMM_INT*”, for the 82527 is sent to the TGPG. To activate the control signals to the axial drive, the appropriate terminals on the axial drive need to be shorted together. Since the signals are polarized, optocouplers with transistor output stages are used to short the terminals together.

Note that the axial drive enable signal is forced inactive by any one of these signals: an overspeed condition, the watchdog circuit being inactive, a disabled axial drive enable switch, an open loop contactor or an axial drive fault. The feedback signals provided by the axial drive are contact closures which must be detected. The input of a Schmidt Trigger is tied by resistor to either power or ground such that the output is inactive. When the contact is closed the input to the Schmidt Trigger is pulled such that the output is active.

For the new axial driver interface, the axial drive is commanded by the firmware via CAN network too. But compared with conventional interface, it doesn’t need 12V power supply from axial driver. TGPG just need to connect on board CAN ground to the axial driver can ground. The axial CAN and control signals to the axial drive are optically isolated from rest of the TGPG and use the +5V isolated power for the output stages of the optoisolators. The CAN bus signals are processed the same as conventional interface CAN bus.

And compared with conventional interface, there are some new control signals. One is used to indicate axial driver fault to TGPG and one is used to send fault reset signal to driver and the other one is used to enable axial driver STO.

The CPU receives signals from thermal sensors: one (LM35DM) is located on the board itself, and the other (LM35DP) is located outside the board.

• Temperature measurement range: 5 – 65.0 degrees C

• Accuracy: +/- 1.0 degree C The signals are converted to digital data by the CPU built-in A/D converter

The TGPG will be able to measure the Gantry Balance using 2 separate piezoelectric devices that indicate a difference in voltage due to the vibrations it senses. These voltages will be amplified on the TGPG and then send to the A/D component.

A +24Vdc input signal from the PDU that indicates the customer room door interlock is open. This signal dynamically tracks the status of the interlock circuit on the TGPG.

A phase under voltage / open fuse detection circuit on the PDU Control board shall monitor the status of the three fuses described above. If the voltage w.r.t. ground on any one or more phases drops below 185Vac (~70% of nominal) the PDU Control board shall detect and latch a PH_LOSS_UV condition and shall issue a "PHASE_LOSS" fault signal to the system.. If contactors Kxg and/or Kss (described above) are closed, the control board shall open them.

A Buss Fault detection circuit on the PDU Control board shall monitor the status of the HVDC. If the differential buss voltage does not exceed 200Vdc within the first 200mS after turn-on the PDU Control board shall detect and latch a BS_FLT condition and shall issue a "BUSS_FLT" fault signal to the system. If contactors Kxg and/or Kss (described above) are closed, the control board shall open them.

Latched +24Vdc output signal to Gantry that indicates the input transformer has overheated. The Control Board will automatically trip CB1 and shut down the system after the assertion of this signal. Cycling power resets this latched fault signal.

Steady-state +24Vdc input signal from the Gantry to indicate the HVDC Bus is enabled. Used by service to bypass firmware control and allow manual control of the HVDC Bus within the NGPDU.

Tilt position feedback is provided by a 5-turn potentiometer.

TGPG provide an interface to tilt inclinometer, which has the similar function as Potentiometer. The inclinometer has an SSI interface to provide digital information to TGPG. TGPG sends out clock signal to inclinometer and it send back the digital data according the received clock. There are total 13 bits to show the gantry angle, which means 1LSB is about 0.044 Deg.

Sensors are mounted on the front and rear of the gantry. When the sensors are not pressed the impedance is 20k Ohms. When the sensor is pressed, the resistance becomes near 0 Ohms. This signal will be decoded on the board, first to indicate that the maximum impedance of the sensor is 40k Ohms (fault condition). Second that the sensor is not a short circuit (interference condition). This is done for both the front and rear sensors. This information is passed through a register on the TGPG board. If there is interference or a fault condition both elevation and tilt will be disabled.

The TGPG board will intercept the signals that currently go to the tilt elevation amp form the TGPG board. The signals required for generating tilt (forward and backward) will be decoded and sent to the tilt relay board. Also the signal enabling elevation will also be intercepted and another enable will be created so that the TGPG board can disable elevation if the interference sensor is in fault or interference is detected.

The operator will be able to prescribe a tilt command from the GSCB Board. The Prescribed Tilt board (2269601) detects the status of the push button, either pressed or released, in the GSCB keyboard by the use of two independent paths. Only one hardware line and now the serial communication will be used. There are still two paths for redundancy, but one by firmware and other by hardware.These two paths would be detected and used to tilt or not tilt. Once the signals are received the redundant path will be sent or transmitted to the TGPG board so that a single point of failure cannot cause tilt motion. The defined voltage level of the prescribed tilt signal shall not be greater than 5vdc. The prescribed tilt signal will maintain active as long as the button is pressed.

The TGPG will receive one hardware signal lines and a serial to initiate remote tilt. When both signal lines are active, a signal is sent to the processor. The processor must check for a stuck button condition. There will also be a line that will indicate fault status of the prescribed tilt input to the board

Tape switches have been added to the tilting base of the gantry to detect if cables on the rotating base are contacting the tilting base. The tape switches will provide an interrupt to the TGPG when the switches are actuated.