Trajectory Generator

To ensure repeatability of measurements, trajectories are a fundamental tool. The present software module can generate setvalues based on defined grid points and simplify the operational management of the system. Various interpolation methodologies, generation options and start/stop behaviors are available to customize operation control.

Fig. 304 Example-Trajectory Example-Trajectories on the JavaScope - Linear interpolation red . Zero-Order-Hold orange

Setup

Defines

Inside the uz_Trajectory.h is a define , which limits the maximum number of samples. This must first be set to the desired number of data points before the module can be configured.

MAX_TRAJECTORY_SAMPLES

Maximum number of samples that can be stored. Should be as small as possible to save resources.

Struct

Struct to store the desired configuration.

typedef struct uz_Trajectory_t uz_Trajectory_t

Object definition for uz_Trajectory_t.

Configuration

The trajectory generator is able to use different interpolation algorithms between the single data points. Currently, only no interpolation (zero-order hold) or linear interpolation is implemented.

enum uz_Trajectory_interpolation_selection

enum for readable configuration of the interpolation type

Values:

enumerator Zero_Order_Hold

enumerator Linear

Select the unit of the time base. The values for time are durations, so only values greater than zero will result in correct behavior.

enum uz_Trajectory_XTicks_selection

enum for readable configuration of the X-Axis-Style

Values:

enumerator ISR_Ticks

enumerator MicroSeconds

enumerator MilliSeconds

enumerator Seconds

Switch to force the generator to repeat the sequence infinitely or a specified number of times.

enum uz_Trajectory_Repeat_selection

enum for readable configuration of the repeat behavior

Values:

enumerator Repeat_Times

enumerator Repeat_Inf

Switch for setting the output behavior. It is possible to hold the last value or a defined zero point when the trajectory has stopped or passed through.

enum uz_Trajectory_Stop_Output_selection

enum for readable configuration of the output behavior

Values:

enumerator ForceToZero

enumerator HoldLast

Config struct to create the trajectory generator

struct uz_Trajectory_config

configuration struct for a trajectory generator.

Public Members

enum uz_Trajectory_interpolation_selection selection_interpolation

Interpolation type selection

enum uz_Trajectory_XTicks_selection selection_XAxis

X-Axis-Style selection

enum uz_Trajectory_Stop_Output_selection StopStyle

Defines the behavior when reaching the end or trajectory is stopped

enum uz_Trajectory_Repeat_selection RepeatStyle

Defines whether the playback process is to be repeated x times or infinitely

uint32_t Number_Sample_Points

Number of samples of the signal to be used. Can be used to display only the first X values.

If this feature isn’t needed, set his value to MAX_TRAJECTORY_SAMPLES

float Sample_Amplitude_Y[MAX_TRAJECTORY_SAMPLES]

Y-Axis-Amplitude of the signal

float Sample_Duration_X[MAX_TRAJECTORY_SAMPLES]

X-Axis-Duration of each Sample of the signal

uint32_t Repeats

Number of repeats

float Stepwidth_ISR

Time of the Stepwidth in with the Trajectory is called

Example

Listing 168 Example configuration for the red Trajectory

#include "uz/uz_Trajectory/uz_Trajectory.h"
int main(void) {
  struct uz_Trajectory_config Trace1_Config = {
    .selection_interpolation = Linear,
    .selection_XAxis = MilliSeconds,
    .StopStyle = HoldLast,
    .RepeatStyle = Repeat_Times,
    .Number_Sample_Points = 11.0f,
    .Sample_Amplitude_Y = {0.0f, 4.0f, 6.0f, 7.0f, 7.5f, 9.0f, 20.0f, 20.0f, -20.0f, 20.0f, 20.0f},
    .Sample_Duration_X = {1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f, 1000.0f , 1000.0f},
    .Repeats = 2,
    .Stepwidth_ISR = (1.0f / UZ_PWM_FREQUENCY) * (Interrupt_ISR_freq_factor)
  };
}

Init function

uz_Trajectory_t *uz_Trajectory_init(struct uz_Trajectory_config config)

Initialization of the Trajectory object.

Parameters:

• config – uz_Trajectory_config configuration struct

Returns:

Pointer to uz_Trajectory_t object

Example

Listing 169 Example function call to init the Trajectory Generator. config according to configuration section

int main(void) {
  uz_Trajectory_t* Traj_instance = uz_Trajectory_init(Traj_config);
}

Description

Allocates the memory for the trajectory generator instance. Furthermore the input values of the configuration struct are asserted.

Functions

Predefined functions are available for easier operation. The Start, Stop and Reset functions can be called directly from the ipc_ARM.c file and should be used to control the trajectory generator.

Start

void uz_Trajectory_Start(uz_Trajectory_t *self)

Starts the trajectory.

Parameters:

• self – pointer to uz_Trajectory_t object

Example

Listing 170 Example function call for a Trajectory-Start

#include "uz/uz_Trajectory/uz_Trajectory.h"
void ipc_Control_func(uint32_t msgId, float value, DS_Data *data){
  ...
  case (My_Button_2):
    ultrazohm_state_machine_set_userLED(true);
    uz_Trajectory_Start(Global_Data.objects.TraceGen_1);
    break;
  ...
}

Stop

void uz_Trajectory_Stop(uz_Trajectory_t *self)

Stops the trajectory.

Parameters:

• self – pointer to uz_Trajectory_t object

Example

Listing 171 Example function call for a Trajectory-Stop

#include "uz/uz_Trajectory/uz_Trajectory.h"
void ipc_Control_func(uint32_t msgId, float value, DS_Data *data){
  ...
  case (My_Button_3):
    ultrazohm_state_machine_set_userLED(false);
    uz_Trajectory_Stop(Global_Data.objects.TraceGen_1);
    break;
  ...
}

Reset

void uz_Trajectory_Reset(uz_Trajectory_t *self)

Resets the trajectory.

Parameters:

• self – pointer to uz_Trajectory_t object

Example

Listing 172 Example function call for a Trajectory-Reset

#include "uz/uz_Trajectory/uz_Trajectory.h"
void ipc_Control_func(uint32_t msgId, float value, DS_Data *data){
  ...
  case (My_Button_4):
    ultrazohm_state_machine_set_userLED(false);
    uz_Trajectory_Reset(Global_Data.objects.TraceGen_1);
    break;
  ...
}

The Step-function should be called from the ISR inside the file isr.c.

Step

float uz_Trajectory_Step(uz_Trajectory_t *self)

Outputs the calculated trajectory.

Parameters:

• self – pointer to uz_Trajectory_t object

Returns:

float Returns current trajectory step

Example

Listing 173 Example function call for a Trajectory-Step

#include "uz/uz_Trajectory/uz_Trajectory.h"
void ISR_Control(void *data){
  ...
  // Generate Trajectory
  Global_Data.av.Traj_1 = uz_Trajectory_Step(Global_Data.objects.TraceGen_1);
  ...
}

Usecase

To create a trajectory with the generator module and use it in operation, the following steps must be followed:

1. Define the needed trajectory and determine the grid points.

2. Define the Samples inside the uz_trajectory.h.

3. Write the configuration and create the trajectory generator object.

   • If the complete trajectory is to be played back, the value config.Number_Sample_Points can be set to the define MAX_TRAJECTORY_SAMPLES. Otherwise, the first X grid points can be played with the value config.Number_Sample_Points.

4. Add the functions uz_Trajectory_Start, uz_Trajectory_Stop and uz_Trajectory_Reset to the IPC-Handler.

   • It is recommended to define some buttons of the JavaScope to control the trajectory generator and to label the buttons according to the programmed functionality.

5. Add the function uz_Trajectory_Step to the ISR and create a variable for the trajectory inside the Global_Data.

6. Add the Output of the trajectory generator to the Global_Data and the JavaScope.

7. Compile the Code and Start the UltraZohm.

After you set up the trajectory generator, you can control the behavior using the JavaScope buttons and play your own trajectories. To do this, first call the start function. The generator will start playing the trajectory until the termination condition is reached or continue doing so indefinitely. The trajectory can be stopped with the Stop function. If the trajectory is to be continued, the start function must be called up again. When the end of the trajectory is reached in repeat mode, the generator locks automatically to prevent an accidental second run. If a second run is desired, the trajectory must first be unlocked with the Reset function.

Designed by

Robert Zipprich (University of Kassel Kassel / EMA) in 10/2023