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2019.12.17 - Hazard System (Potentially Breaking) Changes

Misty’s 2019.12.17 system update includes firmware changes that reduce the frequency of range time-of-flight (ToF) polling in Misty’s firmware. These changes improve the stability of Misty’s ToF readings, which, in turn, improves the performance of Misty’s hazard system.

Because the latency for ToF readings is higher, Misty needs more time to react to the obstacles in her path. To give her the time she needs, this update also increases the default distance threshold for Misty’s range ToF hazards from 150mm to 215mm.

After this change, Misty’s hazard system is less likely to trigger in error and cause the robot to ignore drive commands when there is no obstacle in her path. In most cases, this change will only present itself as a better experience driving your Misty II. However, if you have built skills or applications that rely on these default values, you may observe unexpected behaviors with your code after Misty takes this update.

To solve for and work around these changes, you can:

  • Recommended long-term solution: Update the code for your skill or robot application to reflect the new default distance threshold of 215mm for Misty’s range ToF sensors.
  • Workaround: Use the UpdateBaseHazardManagementSettings command to return the hazard system settings to its prior default settings. Note: When using these default settings, Misty is more likely to collide with obstacles while driving at her top speeds.

A few notes:

  • This change does not affect the sample rate or hazard threshold for Misty’s edge (downward-facing) ToF sensors
  • These changes ameliorate the effects of increased range ToF latency, but do not eliminate them altogether. Misty may sometimes collide with obstacles when driving at top speeds. The likelihood of these collisions is higher when Misty drives in reverse, as Misty is less likely to detect obstacles behind her with her single rear-facing sensor.

While we typically prefer to message breaking changes several weeks in advance of performing a system update, this is an exception. These changes were originally scheduled for Misty’s next system update; however, we felt the performance improvements to be significant enough – and the probability of breaking deployed solutions to be low enough – that we wanted to make the enhancements available as quickly as possible. We apologize for any frustration and headaches this unexpected change will cause. If you need help updating your solution, we’re more than happy to help. Let us know by responding to this thread or send a message to support@mistyrobotics.com.