AWR1642BOOST: Query on velocity of tracked objects

Hi Sreenath,

The velocity resolution for SRR is given by the macro SUBFRAME_SRR_CHIRPTYPE_0_VEL_RESOLUTION_M_P_S. I'm not exactly sure what this evaluates to; perahps a debug print statement would make that clear on your end, or you could manually try evaluating the macro.

As for the doppler velocity question, could you point me to the section of code corresponding to this? I couldn't find this in code.

Regards,

Aayush

Hi,

  For doppler velocity question

Line 618 in "C:\ti\mmwave_automotive_toolbox_2_5_0\labs\lab0002_short_range_radar\gui\read_serial_port_and_plot_object_location.m"

BR

Sreenath

Hi,

Thank you for your prompt reply!

1) A clarification on the above :

So how is the above equation true?

2)Just a query regarding a trend we observed in doppler velocity of a particular tracked vehicle, we saw a sudden jump of velocity by about 0.5m/s between two points(marked in red) even when there was no significant acceleration/deceleration.

What could be the reason?

BR

Sreenath

Hi Sreenath,

For 1, as far as I know, vx and vy from the tracker account for both radial and tangential velocity. Your equations don't take that into account. In my diagram, I had summed the component of vx and vy in the radial direction to get radial velocity. I could do the same in the tangential direction to get the tangential velocity.

I will bring up point 2 with the wider team and see if anyone has seen this tracker behavior before. I will get back to you.

Regards,

Aayush

Hi Aayush,

For 1,Can you please elaborate on that point with a help of a diagram as I couldn't understand.

1)As per our understanding ,Vx - x component of radial velocity and Vy is y component of radial velocity?Is it correct?

   OR 

   Is Vx - radial velocity and Vy-tangential velocity?

2)If Vx is radial velocity , then why do we do summation to get radial velocity again.?

BR,

Sreenath

Hi Sreenath,

SREENATH VIPIN said:

As per our understanding ,Vx - x component of radial velocity and Vy is y component of radial velocity?Is it correct?

   OR 

   Is Vx - radial velocity and Vy-tangential velocity?

I see where the confusion stems from. Neither of these views of Vx, Vy is correct. Perhaps my original, hastily drawn diagram didn't help with this either. Allow me to explain everything with a clean slate.

Actual picture:

1. V is the actual velocity of the object
2. Vx, Vy reported by tracker are components of the object velocity along X and Y axis respectively. This is the same X, Y axis used for the pointcloud's distance data.
3. Velocity V of object can also be represented by the components Vr, Vt (Vradial, Vtangential). Here, the radial direction is the direction of the line joining the radar to the object.
4. The doppler velocity reported by the radar via pointcloud is only the radial component of the object velocity, Vr. This is because the doppler processing method cannot give any information about the tangential velocity, Vt.

So, Vx and Vy reported by the tracker are not components of the radial velocity, rather they are components of the actual object velocity along the X and Y axes. Along with doppler velocity, the tracker also takes into account how the distance of a tracked object changes over time. This is how it can estimate Vx, Vy components of the object's velocity.

So essentially, Vx, Vy are components of V in the X-Y coordinate system; Vr, Vt are components of V in the radial-tangential coordinate system.

With this in mind, converting between these two is a simple coordinate transformation, which can be done with geometry.

Here are the calculations for writing Vx, Vy, Vr, Vt in terms of V, angle of object (theta-o), angle of object velocity(theta-v):

These calculations also show how to write Vr, Vt (Vt not shown) in terms of Vx, Vy, x, y.

Regards,

Aayush

Hi Aayush,

Thank you for the well explained response on doppler velocity equation.

Hope to hear about the doppler velocity trend  of  tracked vehicle as well.

BR,

Sreenath

Hi Sreenath,

Unfortunately, I haven't heard back from the team on the tracking velocity jump issue. I am not sure if this is known to them. Let me see if I can talk to someone with a greater expertise in the SRR tracker about this. I will get back to you by the end of this week.

Regards,

Aayush

Sreenath,

I spoke with the developer of the lab. He says that while he has never seen behavior like this, one reason behind these sudden jumps in tracker velocity could be that the tracker is unable to track the targets velocity as it changes. There is code in the tracking algorithm (i.e. the EKF) that resets the tracker to the measurement if it deviates too much.

I am not sure if this applies to your case, but I can't think of any other reasons for this behavior.

Regards,

Aayush

Hi Aayush,

From CCS firmware of SRR , given by the macro SUBFRAME_SRR_CHIRPTYPE_0_VEL_RESOLUTION_M_P_S,

Velocity Resolution(m/s) computes to approximately 0.52m/s.

Can this be the reason we see a velocity jump?

BR

Sreenath

Hi Sreenath,

That is interesting. Could you compare this with the pointcloud doppler velocity? Since the doppler velocity is measured discretely (in doppler bin index), it will be in multiples of velocity resolution for sure.

I am not sure if it can be expected of the tracker velocity to have more resolution than the input itself (the doppler velocity).

Regards,

Aayush

Hi Aayush,

A similar trend is seen while we did multiple trials and extracted tracker velocity.

By "pointcloud doppler velocity" do you mean the velocity information obtained from detected object tlv?

BR,

Sreenath

Hi Sreenath,

Sorry I accidentally clicked the "TI Thinks Resolved" button.

Yeah, I meant the detected object velocity. You should see the same jump, since that velocity is a multiple of the velocity resolution.

The jumps due to the velocity being a multiple of the detected object TLV velocity is probably also causing the tracker velocity to jump.

Regards,

Aayush

Hi Aayush,

What could be the reason we see the same jump in detected object velocity?

Is there any solution to that velocity jump?

BR

Sreenath