• 1. LHM
  • 1.1. Roadmap
  • 1.2. Mavlink message
    • 1.2.1. Send commands to LHM
    • 1.2.2. LHM command feedback
    • 1.2.3. LHM status report
    • 1.2.4. LHM Command and status
• 2. OLAM
  • 2.1. Roadmap
    • 1.2.1. Send commands to OLAM
    • 1.2.2. OLAM command feedback
    • 1.2.3. LHM status report
    • 1.2.4. OLAM Command and status

1. LHM

1.1. Roadmap

Item	State	To do
Servo control	Completed
Hook control	Completed
Hinge functions	Completed
Serial port communication	Completed
Mavlink communiation	Completed
Status visual aid	In progress	- add more LED stats
Onboard button functions	Completed
Lab test	Completed
LHM mission finish feedback	Not started
Field test	Not started

1.2. Mavlink message

1.2.1. Send commands to LHM

Mavlink protocol is used to handle communication between the LHM and the GCS. The Component ID of LHM is MAV_COMP_ID_USER31 = 55.

To request LHM to perform certain task, GCS needs to send a BUTTON_CHANGE (#2575) message.

Field Name	Type	Values	Description
time_boost_ms	uint32_t	1	Timestamp (time since system boot).
last_change_ms	uint32_t	64218375	Used as a passcode that confirms the message is sent to LHM from GCS
state	uint8_t	LHM Command	The command to be sent.

1.2.2. LHM command feedback

LHM sends command feedback on two occassions: 1. Upon reception of BUTTON_CHNGE 2. Once LHM system starts to execute the command.

Command feedback is reported using COMMAND_ACK (#77).

Field Name	Type	Values	Description
command	uint16_t	LHM Command	The command to be acknowledged.
result	uint8_t	0, 1	Result of command, 0 is failed and 1 is successful.
progress	uint8_t	0, 1, 2, 3	0: Error (not implemented), 1: command_int received and interpreted, 2: mission started, 3: mission finished (not implemented)
result_param2	int32_t		Not used.
target_system	uint8_t		System ID of the target recipient. This is the ID of the system that sent the command for which this COMMAND_ACK is an acknowledgement.
target_component	uint8_t		Component ID of the target recipient. This is the ID of the system that sent the command for which this COMMAND_ACK is an acknowledgement.

1.2.3. LHM status report

LHM reports its status using DEBUG_VECT (#250) at a rate of 1Hz (can be configured).

Field Name	Type	Values	Description
name	char[10]	"LHMS"	Name - used to identify different DEBUG_VECT.
time_usec	uint64_t		Timestamp (unit: us) (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude of the number.
x	float	Hinge status	Status of the hinge.
y	float	Hook status	Status of the hook.
z	float	0, 1	Payload engagement. 0 - not engaged, 1 - engaged.

1.2.4. LHM Command and status

Table 1 LHM Command

Value	Command	Description
60	Hinge - power off	Turn off servo holding torque
61	Hinge - take-off mode	Commands the LHM to prepare for take off.
62	Hinge - landing mode	Commands the LHM to prepare for landing.
63	Hinge - swing reduction mode	Commands the LHM to reduce swing during flight.
65	Hook - power off	Turn off holding torque for the hook servo
66	Hook - close	Lock the hook in closed position
67	Hook - open	Unlock the hook so it opens freely by the weight of the payload.
71	Reset	Reset the controller
~~98	Lock LHM	Lock LHM in payload bay ~~
~~99	Jettison	Jettison the LHM in an emergency~~

Table 2 LHM Hinge status

Value	Status	Description
0	Unknown	Placeholder currently not reachable.
1	Offline	At least one of the two servos is not powered.
2	Error	Servo command not fully executed.
10	Motor torque off	Turn off servo torque.
20	Take-off mode	Hinge is in take-off mode.
30	Landing mode in transition	Hinge is moving into position for landing.
31	Landing mode in position	Hinge is prepared for landing.
40	Swing reduction mode	Hinge is in swing reduction mode.

Table 3 LHM Hook status

Value	Status	Description
0	Unknown	Placeholder, currently not reachable.
1	Offline	At least one device is not powered (microswitches, PE sensor, hook servo)
2	Error	Can be trigger by one of the followings: 1. Servo command not fully executed. 2. Combination of the microswitch states are invalid (both microswitches are triggered) 3. PE sensor state is invalid.
10	Fully closed	Hook is locked in closed state, payload cannot drop out.
11	Fully open	Lock released, hook can be opened by slight force or the weight of the payload, used to drop the payload.
12	Loose (static, in between the previous two states)	Not fully closed nor fully open and hook motor is also static. This is usually unexpected.
20	In transition - Closing	Hook is loose but is being closed and locked.
21	In transition - Opening	Hook is loose but is being opened.

2. OLAM

2.1. Roadmap

Item	State	To do
Servo control	Completed
Tension control	Completed
More intelligent tension control	Completed
Serial port communication	Completed
Mavlink communiation	In progress
Status visual aid	Not started
Onboard button functions	Completed
Lab test	Not started
Field test	Not started

1.2.1. Send commands to OLAM

Mavlink protocol is used to handle communication between the LHM and the GCS. The Component ID of LHM is MAV_COMP_ID_USER31 = 55.

To request LHM to perform certain task, GCS needs to send a BUTTON_CHANGE (#2575) message.

Field Name	Type	Values	Description
time_boost_ms	uint32_t	1	Timestamp (time since system boot).
last_change_ms	uint32_t	32467892	Used as a passcode that confirms the message is sent to LHM from GCS
state	uint8_t	OLAM Command	The command to be sent.

1.2.2. OLAM command feedback

LHM sends command feedback on two occassions: 1. Upon reception of BUTTON_CHNGE 2. Once OLAM system starts to execute the command.

Command feedback is reported using COMMAND_ACK (#77).

Field Name	Type	Values	Description
command	uint16_t	OLAM Command	The command to be acknowledged.
result	uint8_t	0, 1	Result of command, 0 is failed and 1 is successful.
progress	uint8_t	0, 1, 2, 3	0: Error (not implemented), 1: command_int received and interpreted, 2: mission started, 3: mission finished (not implemented)
result_param2	int32_t		Not used.
target_system	uint8_t		System ID of the target recipient. This is the ID of the system that sent the command for which this COMMAND_ACK is an acknowledgement.
target_component	uint8_t		Component ID of the target recipient. This is the ID of the system that sent the command for which this COMMAND_ACK is an acknowledgement.

1.2.3. LHM status report

LHM reports its status using DEBUG_VECT (#250) at a rate of 1Hz (can be configured).

Field Name	Type	Values	Description
name	char[10]	"LHMS"	Name - used to identify different DEBUG_VECT.
time_usec	uint64_t		Timestamp (unit: us) (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude of the number.
x	float	Line status	Status of the hinge.
y	float	Operation Mode	Operation mode of the OLAM.
z	float	0	Not used.

1.2.4. OLAM Command and status

Table 4 OLAM Command

Value	Command	Description
60	Hinge - power off	Turn off servo holding torque
61	Hinge - take-off mode	Commands the LHM to prepare for take off.
62	Hinge - landing mode	Commands the LHM to prepare for landing.
63	Hinge - swing reduction mode	Commands the LHM to reduce swing during flight.
65	Hook - power off	Turn off holding torque for the hook servo
66	Hook - close	Lock the hook in closed position
67	Hook - open	Unlock the hook so it opens freely by the weight of the payload.
71	Reset	Reset the controller
~~98	Lock LHM	Lock LHM in payload bay ~~
~~99	Jettison	Jettison the LHM in an emergency~~

Table 2 LHM Hinge status

Value	Status	Description
0	Unknown	Placeholder currently not reachable.
1	Offline	At least one of the two servos is not powered.
2	Error	Servo command not fully executed.
10	Motor torque off	Turn off servo torque.
20	Take-off mode	Hinge is in take-off mode.
30	Landing mode in transition	Hinge is moving into position for landing.
31	Landing mode in position	Hinge is prepared for landing.
40	Swing reduction mode	Hinge is in swing reduction mode.

Table 3 LHM Hook status

Value	Status	Description
0	Unknown	Placeholder, currently not reachable.
1	Offline	At least one device is not powered (microswitches, PE sensor, hook servo)
2	Error	Can be trigger by one of the followings: 1. Servo command not fully executed. 2. Combination of the microswitch states are invalid (both microswitches are triggered) 3. PE sensor state is invalid.
10	Fully closed	Hook is locked in closed state, payload cannot drop out.
11	Fully open	Lock released, hook can be opened by slight force or the weight of the payload, used to drop the payload.
12	Loose (static, in between the previous two states)	Not fully closed nor fully open and hook motor is also static. This is usually unexpected.
20	In transition - Closing	Hook is loose but is being closed and locked.
21	In transition - Opening	Hook is loose but is being opened.